Oracle Linux 5 Security Technical Implementation Guide

The /etc/gshadow file is critical to system security and must be owned by a privileged user. The /etc/gshadow file contains a list of system groups and hashes for group passwords.

The /etc/gshadow file is critical to system security and must be protected from unauthorized modification. The /etc/gshadow file contains a list of system groups and hashes for group passwords.

Group passwords are typically shared and should not be used.

Without the correct options enabled, the Xwindows system would be less secure and there would be no screen timeout.

The /etc/security/access.conf file contains entries restricting access from the system console by authorized System Administrators. If the file is owned by a user other than root, it could compromise the system.

If the access permissions are more permissive than 0640, system security could be compromised.

The sysctl.conf file specifies the values for kernel parameters to be set on boot. These settings can affect the system's security.

The sysctl.conf file specifies the values for kernel parameters to be set on boot. These settings can affect the system's security.

Insecure file locking could allow for sensitive data to be viewed or edited by an unauthorized user.

If an unauthorized user has been granted privileged access while logged in at the console, the security posture of a system could be greatly compromised. Additionally, such a situation could deny legitimate root access from another terminal.

The securetty file contains the list of terminals permitting direct root logins. It must be protected from unauthorized modification.

If auditing is enabled late in the boot process, the actions of startup scripts may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

If the system does not require valid root authentication before it boots into single-user or maintenance mode, anyone who invokes single-user or maintenance mode is granted privileged access to all files on the system.

Timely patching is critical for maintaining the operational availability, confidentiality, and integrity of information technology (IT) systems. However, failure to keep operating system and application software patched is a common mistake made by IT professionals. New patches are released daily, and it is often difficult for even experienced system administrators to keep abreast of all the new patches. When new weaknesses in an operating system exist, patches are usually made available by the vendor to resolve the problems. If the most recent security patches and updates are not installed, unauthorized users may take advantage of weaknesses present in the unpatched software. The lack of prompt attention to patching could result in a system compromise.

A file integrity baseline is a collection of file metadata which is to evaluate the integrity of the system. A minimal baseline must contain metadata for all device files, setuid files, setgid files, system libraries, system binaries, and system configuration files. The minimal metadata must consist of the mode, owner, group owner, and modification times. For regular files, metadata must also include file size and a cryptographic hash of the file's contents.

To assure the accuracy of the system clock, it must be synchronized with an authoritative time source within DoD. Many system functions, including time-based login and activity restrictions, automated reports, system logs, and audit records depend on an accurate system clock. If there is no confidence in the correctness of the system clock, time-based functions may not operate as intended and records may be of diminished value.

Authoritative time sources include authorized time servers within the enclave that synchronize with upstream authoritative sources. Specific requirements for the upstream synchronization of network time protocol (NTP) servers are covered in the Network Other Devices STIG.

For systems located on isolated or closed networks, it is not necessary to synchronize with a global authoritative time source. If a global authoritative time source is not available to systems on an isolated network, a local authoritative time source must be established on this network and used by the systems connected to this network. This is necessary to provide the ability to correlate events and allow for the correct operation of time-dependent protocols between systems on the isolated network.

If the system is completely isolated (i.e., it has no connections to networks or other systems), time synchronization is not required as no correlation of events between systems will be necessary. If the system is completely isolated, this requirement is not applicable.

A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. For redundancy, two time sources are required so synchronization continues to function if one source fails.

If the system is completely isolated (i.e., it has no connections to networks or other systems), time synchronization is not required as no correlation of events or operation of time-dependent protocols between systems will be necessary. If the system is completely isolated, this requirement is not applicable.

Note: For the network time protocol (NTP), the requirement is two servers, but it is recommended to configure at least four distinct time servers which allow NTP to effectively exclude a time source not consistent with the others. The system's local clock must be excluded from the count of time sources.

A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not owned by a system account, unauthorized modifications could result in the failure of time synchronization.

A synchronized system clock is critical for the enforcement of time-based policies and the correlation of logs and audit records with other systems. If an illicit time source is used for synchronization, the integrity of system logs and the security of the system could be compromised. If the configuration files controlling time synchronization are not protected, unauthorized modifications could result in the failure of time synchronization.

Shared accounts (accounts where two or more people log in with the same user identification) do not provide identification and authentication. There is no way to provide for non-repudiation or individual accountability.

Accounts that provide no operational purpose provide additional opportunities for system compromise. Unnecessary accounts include user accounts for individuals not requiring access to the system and application accounts for applications not installed on the system.

Accounts that provide no operational purpose provide additional opportunities for system compromise. Unnecessary accounts include user accounts for individuals not requiring access to the system and application accounts for applications not installed on the system.

A unique user name is the first part of the identification and authentication process. If user names are not unique, there can be no accountability on the system for auditing purposes. Multiple accounts sharing the same name could result in the denial of service to one or both of the accounts or unauthorized access to files or privileges.

Reserved UIDs are typically used by system software packages. If non-system accounts have UIDs in this range, they may conflict with system software, possibly leading to the user having permissions to modify system files.

If a user is assigned the GID of a group not existing on the system, and a group with the GID is subsequently created, the user may have unintended rights to the group.

Failure to display the logon banner prior to a logon attempt will negate legal proceedings resulting from unauthorized access to system resources.

This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices as well as to graphical desktop environments provided to remote systems, including thin clients.

Monitoring and recording successful and unsuccessful logins assists in tracking unauthorized access to the system. Without this logging, the ability to track unauthorized activity to specific user accounts may be diminished.

Providing users with feedback on when account accesses last occurred facilitates user recognition and reporting of unauthorized account use.

Enforcing a delay between successive failed login attempts increases protection against automated password guessing attacks.

If graphical desktop sessions do not lock the session after 15 minutes of inactivity, requiring re-authentication to resume operations, the system or individual data could be compromised by an alert intruder who could exploit the oversight. This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices as well as to graphical desktop environments provided to remote systems, including thin clients.

To protect the on-screen content of a session, it must be replaced with a publicly-viewable pattern upon session lock. Examples of publicly viewable patterns include screen saver patterns, photographic images, solid colors, or a blank screen, so long as none of those patterns convey sensitive information.

This requirement applies to graphical desktop environments provided by the system to locally attached displays and input devices, as well as, to graphical desktop environments provided to remote systems using remote access protocols.

The ability to change passwords frequently facilitates users reusing the same password. This can result in users effectively never changing their passwords. This would be accomplished by users changing their passwords when required and then immediately changing it to the original value.

The use of longer passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques by increasing the password search space.

Systems must employ cryptographic hashes for passwords using the SHA-2 family of algorithms or FIPS 140-2 approved successors. The use of unapproved algorithms may result in weak password hashes more vulnerable to compromise.

To enforce the use of complex passwords, minimum numbers of characters of different classes are mandated. The use of complex passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques. Complexity requirements increase the password search space by requiring users to construct passwords from a larger character set than they may otherwise use.

To enforce the use of complex passwords, minimum numbers of characters of different classes are mandated. The use of complex passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques. Complexity requirements increase the password search space by requiring users to construct passwords from a larger character set than they may otherwise use.

To enforce the use of complex passwords, minimum numbers of characters of different classes are mandated. The use of complex passwords reduces the ability of attackers to successfully obtain valid passwords using guessing or exhaustive search techniques. Complexity requirements increase the password search space by requiring users to construct passwords from a larger character set than they may otherwise use.

Limiting the lifespan of authenticators limits the period of time an unauthorized user has access to the system while using compromised credentials and reduces the period of time available for password-guessing attacks to run against a single password.

To ensure password changes are effective in their goals, the system must ensure that old and new passwords have significant differences. Without significant changes, new passwords may be easily guessed based on the value of a previously compromised password.

An easily guessable password provides an open door to any external or internal malicious intruder. Many computer compromises occur as the result of account name and password guessing. This is generally done by someone with an automated script that uses repeated logon attempts until the correct account and password pair is guessed. Utilities, such as cracklib, can be used to validate passwords are not dictionary words and meet other criteria during password changes.

Configuring a supplemental group for users permitted to switch to the root user prevents unauthorized users from accessing the root account, even with knowledge of the root credentials.

Changing the root home directory to something other than / and assigning it a 0700 protection makes it more difficult for intruders to manipulate the system by reading the files root places in its default directory. It also gives root the same discretionary access control for root's home directory as for the other user home directories.

File system extended ACLs provide access to files beyond what is allowed by the UNIX permissions of the files.

The library search path environment variable(s) contain a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon or two consecutive colons, this is interpreted as the current working directory. Entries starting with a slash (/) are absolute paths.

If the root search path contains a world-writable directory, malicious software could be placed in the path by intruders and/or malicious users and inadvertently run by root with all of root's privileges.

The remote console feature provides an additional means of access to the system which could allow unauthorized access if not disabled or properly secured. With virtualization technologies, remote console access is essential as there is no physical console for virtual machines. Remote console access must be protected in the same manner as any other remote privileged access method.

The "sudo" command allows authorized users to run programs (including shells) as other users, system users, and root. The "/etc/sudoers" file is used to configure authorized "sudo" users as well as the programs they are allowed to run. Some configuration options in the "/etc/sudoers" file allow configured users to run programs without re-authenticating. Use of these configuration options makes it easier for one compromised account to be used to compromise other accounts.

To ensure the root shell is available in repair and administrative modes, the root shell must be located in the / file system.

Even though communications are encrypted, an additional layer of security may be gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account preserves the audit trail.

Un-owned files and directories may be unintentionally inherited if a user is assigned the same UID as the UID of the un-owned files.

Restricting permission on daemons will protect them from unauthorized modification and possible system compromise.

Restricting permissions will protect system command files from unauthorized modification. System command files include files present in directories used by the operating system for storing default system executables and files present in directories included in the system's default executable search paths.

Restricting permissions will protect the files from unauthorized modification.

If the system log files are not protected, unauthorized users could change the logged data, eliminating its forensic value.

If manual pages are compromised, misleading information could be inserted, causing actions to compromise the system.

Unauthorized access could destroy the integrity of the library files.

NIS/NIS+/yp files are part of the system's identification and authentication processes and are critical to system security. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.

NIS/NIS+/yp files are part of the system's identification and authentication processes and are critical to system security. Unauthorized modification of these files could compromise these processes and the system.

The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions such as time synchronization, centralized authentication, and remote system logging.

The resolv.conf (or equivalent) file configures the system's DNS resolver. DNS is used to resolve host names to IP addresses. If DNS configuration is modified maliciously, host name resolution may fail or return incorrect information. DNS may be used by a variety of system security functions such as time synchronization, centralized authentication, and remote system logging.

The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

The /etc/hosts file (or equivalent) configures local host name to IP address mappings that typically take precedence over DNS resolution. If this file is maliciously modified, it could cause the failure or compromise of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.

The nsswitch.conf file (or equivalent) configures the source of a variety of system security information including account, group, and host lookups. Malicious changes could prevent the system from functioning or compromise system security.

To provide availability for name resolution services, multiple redundant name servers are mandated. A failure in name resolution could lead to the failure of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

The /etc/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification.

File system ACLs can provide access to files beyond what is allowed by the mode numbers of the files. The /etc/passwd file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification.

The /etc/group file is critical to system security and must be protected from unauthorized modification. The group file contains a list of system groups and associated information.

The /etc/group file is critical to system security and must be protected from unauthorized modification. The group file contains a list of system groups and associated information.

The /etc/shadow file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. The file also contains password hashes which must not be accessible to users other than root.

The /etc/shadow file contains the list of local system accounts. It is vital to system security and must be protected from unauthorized modification. The file also contains password hashes which must not be accessible to users other than root.

If a user has a home directory defined that does not exist, the user may be given the / directory, by default, as the current working directory upon logon. This could create a Denial of Service because the user would not be able to perform useful tasks in this location.

Group passwords are typically shared and should not be used. Additionally, if password hashes are readable by non-administrators, the passwords are subject to attack through lookup tables or cryptographic weaknesses in the hashes.

Excessive permissions on home directories allow unauthorized access to user files.

If the Group Identifier (GID) of the home directory is not the same as the GID of the user, this would allow unauthorized access to files.

If a user's files are group-owned by a group of which the user is not a member, unintended users may be able to access them.

Excessive permissions allow unauthorized access to user files.

If the startup files are writable by other users, they could modify the startup files to insert malicious commands into the startup files.

The library search path environment variable(s) contain a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories. If there is an empty entry, such as a leading or trailing colon, two consecutive colons, or a single period, this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.

World-writable files could be modified accidentally or maliciously to compromise system integrity.

If system start-up files do not have a group owner of root or a system group, the files may be modified by malicious users or intruders.

Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.

Global initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon. Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.

If the "mesg -n" or "mesg n" command is not placed into the system profile, messaging can be used to cause a Denial of Service attack.

If the skeleton files are not protected, unauthorized personnel could change user startup parameters and possibly jeopardize user files.

If the skeleton files are not protected, unauthorized personnel could change user startup parameters and possibly jeopardize user files.

The library search path environment variable(s) contain a list of directories for the dynamic linker to search to find libraries. If this path includes the current working directory or other relative paths, libraries in these directories may be loaded instead of system libraries. This variable is formatted as a colon-separated list of directories, such as a leading or trailing colon, two consecutive colons, or a single period; this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.

Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.

Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon logon.

The executable search path (typically the PATH environment variable) contains a list of directories for the shell to search to find executables. If this path includes the current working directory or other relative paths, executables in these directories may be executed instead of system commands. This variable is formatted as a colon-separated list of directories, such as a leading or trailing colon, two consecutive colons, or a single period; this is interpreted as the current working directory. Paths starting with a slash (/) are absolute paths.

The library preload list environment variable contains a list of libraries for the dynamic linker to load before loading the libraries required by the binary. If an entry begins with a character other than a slash (/), or has If this list contains paths to libraries to the current working directory that have not been authorized, unintended libraries may be preloaded. This variable is formatted as a space-separated list of libraries. Paths starting with a slash (/) are absolute paths.

A plus (+) in system accounts files causes the system to lookup the specified entry using NIS. If the system is not using NIS, no such entries should exist.

If these files are not properly configured, they could allow malicious access by unknown malicious users from untrusted hosts who could compromise the system.

If these files are accessible by users other than root or the owner, they could be used by a malicious user to set up a system compromise.

The shells file (or equivalent) lists approved default shells. It helps provide layered defense to the security approach by ensuring users cannot change their default shell to an unauthorized unsecure shell.

If shell files are owned by users other than root or bin, they could be modified by intruders or malicious users to perform unauthorized actions.

Shells with world/group write permissions give the ability to maliciously modify the shell to obtain unauthorized access.

If an unauthorized device is allowed to exist on the system, there is the possibility the system may perform unauthorized operations.

System backups could be accidentally or maliciously overwritten and destroy the ability to recover the system if a compromise should occur. Unauthorized users could also copy system files.

File system ACLs can provide access to files beyond what is allowed by the mode numbers of the files.

Without privileged group owners, audio devices will be vulnerable to being used as eaves-dropping devices by malicious users or intruders to possibly listen to conversations containing sensitive information.

Files with the setuid bit set will allow anyone running these files to be temporarily assigned the UID of the file. While many system files depend on these attributes for proper operation, security problems can result if setuid is assigned to programs allowing reading and writing of files, or shell escapes.

The "nodev" (or equivalent) mount option causes the system to not handle device files as system devices. This option must be used for mounting any file system not containing approved device files. Device files can provide direct access to system hardware and can compromise security if not protected.

Files with the setgid bit set will allow anyone running these files to be temporarily assigned the group id of the file. While many system files depend on these attributes for proper operation, security problems can result if setgid is assigned to programs allowing reading and writing of files, or shell escapes.

Failing to set the sticky bit on the public directories allows unauthorized users to delete files in the directory structure.

The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage, (e.g., /tmp), and for directories requiring global read/write access.

If a public directory has the sticky bit set and is not group-owned by a privileged GID, unauthorized users may be able to modify files created by others.

The only authorized public directories are those temporary directories supplied with the system or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system and by users for temporary file storage, (e.g., /tmp), and for directories requiring global read/write access.

Vendor accounts and software may contain backdoors allowing unauthorized access to the system. These backdoors are common knowledge and present a threat to system security if the account is not disabled.

Failure to give ownership of system audit log files to root provides the designated owner and unauthorized users with the potential to access sensitive information.

If a user can write to the audit logs, audit trails can be modified or destroyed and system intrusion may not be detected. System audit logs are those files generated from the audit system and do not include activity, error, or other log files created by application software.

To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.

To prevent unauthorized access or manipulation of system audit logs, the tools for manipulating those logs must be protected.

An accurate and current audit trail is essential for maintaining a record of system activity. If the system fails, the SA must be notified and must take prompt action to correct the problem.

Minimally, the system must log this event and the SA will receive this notification during the daily system log review. If feasible, active alerting (such as e-mail or paging) should be employed consistent with the site's established operations management systems and procedures.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

An accurate and current audit trail is essential for maintaining a record of system activity. If the system fails, the SA must be notified and must take prompt action to correct the problem.

Minimally, the system must log this event and the SA will receive this notification during the daily system log review. If feasible, active alerting (such as e-mail or paging) should be employed consistent with the site's established operations management systems and procedures.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

If the system is not configured to audit certain activities and write them to an audit log, it is more difficult to detect and track system compromises and damages incurred during a system compromise.

Actions concerning dynamic kernel modules must be recorded as they are substantial events. Dynamic kernel modules can increase the attack surface of a system. A malicious kernel module can be used to substantially alter the functioning of a system, often with the purpose of hiding a compromise from the SA.

Actions concerning dynamic kernel modules must be recorded as they are substantial events. Dynamic kernel modules can increase the attack surface of a system. A malicious kernel module can be used to substantially alter the functioning of a system, often with the purpose of hiding a compromise from the SA.

Actions concerning dynamic kernel modules must be recorded as they are substantial events. Dynamic kernel modules can increase the attack surface of a system. A malicious kernel module can be used to substantially alter the functioning of a system, often with the purpose of hiding a compromise from the SA.

System/Audit records contain evidence that can be used in the investigation of compromised systems. To prevent this evidence from compromise, it must be sent to a separate system continuously. Methods for sending audit records include, but are not limited to, system audit tools used to send logs directly to another host or through the system's syslog service to another host.

A readable and/or writable cron.allow file by users other than root could allow potential intruders and malicious users to use the file contents to help discern information, such as who is allowed to execute cron programs, which could be harmful to overall system and network security.

If cron executes group-writable or world-writable programs, there is a possibility that unauthorized users could manipulate the programs with malicious intent. This could compromise system and network security.

To protect the integrity of scheduled system jobs and prevent malicious modification to these jobs, crontab files must be secured.

To centralize the management of privileged account crontabs, of the default system accounts, only root may have a crontab.

To protect the integrity of scheduled system jobs and prevent malicious modification to these jobs, crontab files must be secured.

To protect the integrity of scheduled system jobs and to prevent malicious modification to these jobs, crontab files must be secured.

Incorrect ownership of the cron or crontab directories could permit unauthorized users the ability to alter cron jobs and run automated jobs as privileged users. Failure to give ownership of cron or crontab directories to root or to bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration which could weaken the system's security posture.

Cron logging can be used to trace the successful or unsuccessful execution of cron jobs. It can also be used to spot intrusions into the use of the cron facility by unauthorized and malicious users.

Cron logs contain reports of scheduled system activities and must be protected from unauthorized access or manipulation.

If there are excessive file permissions for the cron.deny file, sensitive information could be viewed or edited by unauthorized users.

If the owner of the cron.allow file is not set to root, bin, or sys, the possibility exists for an unauthorized user to view or to edit sensitive information.

If the group of the cron.allow is not set to root, bin, sys, or cron, the possibility exists for an unauthorized user to view or edit the list of users permitted to use cron. Unauthorized modification of this file could cause Denial of Service to authorized cron users or provide unauthorized users with the ability to run cron jobs.

The "at" daemon control files restrict access to scheduled job manipulation and must be protected. Unauthorized modification of the at.deny file could result in Denial of Service to authorized "at" users or provide unauthorized users with the ability to run "at" jobs.

Cron daemon control files restrict the scheduling of automated tasks and must be protected. Unauthorized modification of the cron.deny file could result in Denial of Service to authorized cron users or could provide unauthorized users with the ability to run cron jobs.

On some systems, if there is no at.allow file and there is an empty at.deny file, then the system assumes everyone has permission to use the "at" facility. This could create an insecure setting in the case of malicious users or system intruders.

Permissions more permissive than 0600 (read, write and execute for the owner) may allow unauthorized or malicious access to the at.allow and/or at.deny files.

If "at" programs are located in, or subordinate, to world-writable directories, they become vulnerable to removal and replacement by malicious users or system intruders.

If the "at" directory has an extended ACL, unauthorized users could be allowed to view or to edit files containing sensitive information within the "at" directory. Unauthorized modifications could result in Denial of Service to authorized "at" jobs.

If the group of the "at" directory is not root, bin, sys, or cron, unauthorized users could be allowed to view or edit files containing sensitive information within the directory.

If the owner of the at.allow file is not set to root, bin, or sys, unauthorized users could be allowed to view or edit sensitive information contained within the file.

If the owner of the at.deny file is not set to root, bin, or sys, unauthorized users could be allowed to view or edit sensitive information contained within the file.

Process core dumps contain the memory in use by the process when it crashed. Process core dump files can be of significant size and their use can result in file systems filling to capacity, which may result in Denial of Service. Process core dumps can be useful for software debugging.

Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If the kernel core dump data directory is not owned by root, the core dumps contained in the directory may be subject to unauthorized access.

Kernel core dumps may contain the full contents of system memory at the time of the crash. As the system memory may contain sensitive information, it must be protected accordingly. If the mode of the kernel core dump data directory is more permissive than 0700, unauthorized users may be able to view or to modify kernel core dump data files.

A common type of exploit is the stack buffer overflow. An application receives, from an attacker, more data than it is prepared for and stores this information on its stack, writing beyond the space reserved for it. This can be designed to cause execution of the data written on the stack. One mechanism to mitigate this vulnerability is for the system to not allow the execution of instructions in sections of memory identified as part of the stack.

Source-routed packets allow the source of the packet to suggest routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

The processing of (ICMP) timestamp requests increases the attack surface of the system.

The processing of (ICMP) timestamp requests increases the attack surface of the system. Responding to broadcast ICMP timestamp requests facilitates network mapping and provides a vector for amplification attacks.

Proxy ARP allows a system to respond to ARP requests on one interface on behalf of hosts connected to another interface. If this function is enabled when not required, addressing information may be leaked between the attached network segments.

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table possibly revealing portions of the network topology.

A TCP SYN flood attack can cause Denial of Service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies are a mechanism used to only track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This technique does not operate in a fully standards-compliant manner, but is only activated when a flood condition is detected, and allows defense of the system while continuing to service valid requests.

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

The use of separate file systems for different paths can protect the system from failures resulting from a file system becoming full or failing.

File system journaling, or logging, can allow reconstruction of file system data after a system crash, preserving the integrity of data that may have otherwise been lost. Journaling file systems typically do not require consistency checks upon booting after a crash, which can improve system availability. Some file systems employ other mechanisms to ensure consistency also satisfying this requirement.

Monitoring and recording successful and unsuccessful logins assists in tracking unauthorized access to the system.

Failure to give ownership of sensitive files or utilities to root provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration possibly weakening the system's security posture.

The Internet service daemon configuration files must be protected as malicious modification could cause Denial of Service or increase the attack surface of the system.

The Internet service daemon configuration files must be protected as malicious modification could cause Denial of Service or increase the attack surface of the system.

Failure to give ownership of sensitive files or utilities to root or bin provides the designated owner and unauthorized users with the potential to access sensitive information or change the system configuration possibly weakening the system's security posture.

The services file is critical to the proper operation of network services and must be protected from unauthorized modification. Unauthorized modification could result in the failure of network services.

Inetd or xinetd logging and tracing allows the system administrators to observe the IP addresses connecting to their machines and what network services are being sought. This provides valuable information when trying to find the source of malicious users and potential malicious users.

The portmap and rpcbind services increase the attack surface of the system and should only be used when needed. The portmap or rpcbind services are used by a variety of services using Remote Procedure Calls (RPCs).

The rshd process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.

The rlogind process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.

The rexecd process provides a typically unencrypted, host-authenticated remote access service. SSH should be used in place of this service.

The finger service provides information about the system's users to network clients. This information could expose more information for potential used in subsequent attacks.

Having the '+' character in the hosts.lpd (or equivalent) file allows all hosts to use local system print resources.

Failure to give group-ownership of the hosts.lpd file to root, bin, sys, or system provides the members of the owning group and possible unauthorized users, with the potential to modify the hosts.lpd file. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.

Excessive permissions on the hosts.lpd (or equivalent) file may permit unauthorized modification. Unauthorized modifications could disrupt access to local printers from authorized remote hosts or permit unauthorized remote access to local printers.

If the group owner of the traceroute command has not been set to a system group, unauthorized users could have access to the command and use it to gain information regarding a network's topology inside of the firewall. This information may allow an attacker to determine trusted routers and other network information potentially leading to system and network compromise.

If an extended ACL exists on the traceroute executable file, it may provide unauthorized users with access to the file. Malicious code could be inserted by an attacker and triggered whenever the traceroute command is executed by authorized users. Additionally, if an unauthorized user is granted executable permissions to the traceroute command, it could be used to gain information about the network topology behind the firewall. This information may allow an attacker to determine trusted routers and other network information potentially leading to system and network compromise.

If the alias file is not owned by root, an unauthorized user may modify the file adding aliases to run malicious code or redirect e-mail.

Excessive permissions on the aliases file may permit unauthorized modification. If the alias file is modified by an unauthorized user, they may modify the file to run malicious code or redirect e-mail.

If a file executed through a mail aliases file is not owned and writable only by root, it may be subject to unauthorized modification. Unauthorized modification of files executed through aliases may allow unauthorized users to attain root privileges.

If a file executed through a mail aliases file has permissions greater than 0755, it can be modified by an unauthorized user and may contain malicious code or instructions potentially compromising the system.

If Sendmail is not configured to log at level 9, system logs may not contain the information necessary for tracking unauthorized use of the sendmail service.

If the SMTP service log file is not owned by root, then unauthorized personnel may modify or delete the file to hide a system compromise.

If the SMTP service log file has an extended ACL, unauthorized users may be allowed to access or to modify the log file.

The version of the SMTP service can be used by attackers to plan an attack based on vulnerabilities present in the specific version.

The SMTP service version on the system must be current to avoid exposing vulnerabilities present in unpatched versions.

A common configuration for older Mail Transfer Agents (MTAs) is to include an alias for the decode user. All mail sent to this user is sent to the uudecode program, which automatically converts and stores files. By sending mail to the decode or the uudecode aliases present on some systems, a remote attacker may be able to create or overwrite files on the remote host. This could possibly be used to gain remote access.

The VRFY command allows an attacker to determine if an account exists on a system, providing significant assistance to a brute force attack on user accounts. VRFY may provide additional information about users on the system, such as the full names of account owners.

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay for the purpose of sending SPAM or other unauthorized activity.

Due to the numerous vulnerabilities inherent in anonymous FTP, it is not recommended. If anonymous FTP must be used on a system, the requirement must be authorized and approved in the system accreditation package.

The ftpusers file contains a list of accounts not allowed to use FTP to transfer files. If this file does not exist, then unauthorized accounts can utilize FTP.

If the file ftpusers is not owned by root, an unauthorized user may modify the file to allow unauthorized accounts to use FTP.

Excessive permissions on the ftpusers file could permit unauthorized modification. Unauthorized modification could result in Denial of Service to authorized FTP users or permit unauthorized users to access the FTP service.

The -l option allows basic logging of connections. The verbose (on HP) and the debug (on Solaris) allow logging of what files the ftp session transferred. This extra logging makes it possible to easily track which files are being transferred onto or from a system. If they are not configured, the only option for tracking is the audit files. The audit files are much harder to read. If auditing is not properly configured, then there would be no record at all of the file transfer transactions.

The umask controls the default access mode assigned to newly created files. An umask of 077 limits new files to mode 700 or less permissive. Although umask is stored as a 4-digit number, the first digit representing special access modes is typically ignored or required to be zero (0).

If TFTP runs with the setuid or setgid bit set, it may be able to write to any file or directory and may seriously impair system integrity, confidentiality, and availability.

TFTP is a file transfer protocol often used by embedded systems to obtain configuration data or software. The service is unencrypted and does not require authentication of requests. Data available using this service may be subject to unauthorized access or interception.

.Xauthority files ensure the user is authorized to access specific X Windows host. Excessive permissions may permit unauthorized modification of these files, which could lead to Denial of Service to authorized access or allow unauthorized access to be obtained.

Open X displays allow an attacker to capture keystrokes and to execute commands remotely. Many users have their X Server set to "xhost +", permitting access to the X Server by anyone, from anywhere.

If unauthorized clients are permitted access to the X server, a user's X session may be compromised.

The UUCP utility is designed to assist in transferring files, executing remote commands, and sending e-mail between UNIX systems over phone lines and direct connections between systems. The UUCP utility is a primitive and arcane system with many security issues. There are alternate data transfer utilities/products that can be configured to more securely transfer data by providing for authentication as well as encryption.

SNMP Versions 1 and 2 are not considered secure. Without the strong authentication and privacy provided by the SNMP Version 3 User-based Security Model (USM), an attacker or other unauthorized users may gain access to detailed system management information and use the information to launch attacks against the system.

The SNMP service must use AES or a FIPS 140-2 approved successor algorithm for protecting the privacy of communications.

The ability to read the MIB file could impart special knowledge to an intruder or malicious user about the ability to extract compromising information about the system or network.

The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification. If the file is not owned by root, it may be subject to access and modification from unauthorized users.

The snmpd.conf file contains authenticators and must be protected from unauthorized access and modification.

Unauthorized users must not be allowed to access or modify the /etc/syslog.conf file.

If the /etc/syslog.conf file is not owned by root, unauthorized users could be allowed to view, edit, or delete important system messages handled by the syslog facility.

Syslog messages are typically unencrypted, may contain sensitive information, and are restricted to the enclave.

If a remote log host is in use and it has not been justified and documented with the IAO, sensitive information could be obtained by unauthorized users without the SA's knowledge. A remote log host is any host to which the system is sending syslog messages over a network.

SSHv1 is not a DoD-approved protocol and has many well-known vulnerability exploits. Exploits of the SSH daemon could provide immediate root access to the system.

The SSH daemon should only listen on network addresses designated for management traffic. If the system has multiple network interfaces and SSH listens on addresses not designated for management traffic, the SSH service could be subject to unauthorized access. If SSH is used for purposes other than management, such as providing an SFTP service, the list of approved listening addresses may be documented.

The Cipher-Block Chaining (CBC) mode of encryption as implemented in the SSHv2 protocol is vulnerable to chosen plain text attacks and must not be used.

DoD information systems are required to use FIPS 140-2 approved ciphers. SSHv2 ciphers meeting this requirement are 3DES and AES.

DoD information systems are required to use FIPS 140-2 approved cryptographic hash functions.

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

GSSAPI authentication is used to provide additional authentication mechanisms to applications. Allowing GSSAPI authentication through SSH exposes the system's GSSAPI to remote hosts, increasing the attack surface of the system. GSSAPI authentication must be disabled unless needed.

Kerberos authentication for SSH is often implemented using GSSAPI. If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementation may then be subject to exploitation. To reduce the attack surface of the system, the Kerberos authentication mechanism within SSH must be disabled for systems not using this capability.

If other users have access to modify user-specific SSH configuration files, they may be able to log into the system as another user.

If SSH permits rhosts RSA authentication, a user may be able to log in based on the keys of the host originating the request and not any user-specific authentication.

The SSH daemon must be configured for IP filtering to provide a layered defense against connection attempts from unauthorized addresses.

If a system has no default gateway defined, the system is at increased risk of man-in-the-middle, monitoring, and Denial of Service attacks.

Installing extraneous software on a system designated as a dedicated router poses a security threat to the system and the network. Should an attacker gain access to the router through the unauthorized software, the entire network is susceptible to malicious activity.

If the system is configured for IP forwarding and is not a designated router, it could be used to bypass network security by providing a path for communication not filtered by network devices.

Failure to give ownership of the NFS export configuration file to root provides the designated owner and possible unauthorized users with the potential to change system configuration which could weaken the system's security posture.

Excessive permissions on the NFS export configuration file could allow unauthorized modification of the file, which could result in Denial of Service to authorized NFS exports and the creation of additional unauthorized exports.

Failure to give ownership of sensitive files or directories to root provides the designated owner and possible unauthorized users with the potential to access sensitive information or change system configuration which could weaken the system's security posture.

When an NFS server is configured to deny remote root access, a selected UID and GID are used to handle requests from the remote root user. The UID and GID should be chosen from the system to provide the appropriate level of non-privileged access.

If the NFS server allows root access to local file systems from remote hosts, this access could be used to compromise the system.

Public (IM) systems are not approved for use and may result in the unauthorized distribution of information. IM clients provide a way for a user to send a message to one or more other users in real time. Additional capabilities may include file transfer and support for distributed game playing. Communication between clients and associated directory services are managed through messaging servers. Commercial IM clients include AOL Instant Messenger (AIM), MSN Messenger, and Yahoo! Messenger.

IM clients present a security issue when the clients route messages through public servers. The obvious implication is potentially sensitive information could be intercepted or altered in the course of transmission. This same issue is associated with the use of public e-mail servers. In order to reduce the potential for disclosure of sensitive Government information and to ensure the validity of official government information, IM clients connecting to public IM services will not be installed. Clients use to access internal or DoD-controlled IM services are permitted.

Samba is a tool used for the sharing of files and printers between Windows and UNIX operating systems. It provides access to sensitive files and, therefore, poses a security risk if compromised.

The /etc/smb.conf file allows access to other machines on the network and grants permissions to certain users. If it is owned by another user, the file may be maliciously modified and the Samba configuration could be compromised.

If the "smb.conf" file has excessive permissions, the file may be maliciously modified and the Samba configuration could be compromised.

If the "smbpasswd" file is not owned by root, it may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.

If the smbpasswd file has a mode more permissive than 0600, the smbpasswd file may be maliciously accessed or modified, potentially resulting in the compromise of Samba accounts.

Samba increases the attack surface of the system and must be restricted to communicate only with systems requiring access.

Samba must be configured to protect authenticators. If Samba passwords are not encrypted for storage, plain-text user passwords may be read by those with access to the Samba password file.

INN servers access Usenet newsfeeds and store newsgroup articles. INN servers use the Network News Transfer Protocol (NNTP) to transfer information from the Usenet to the server and from the server to authorized remote hosts.

If this function is necessary to support a valid mission requirement, its use must be authorized and approved in the system accreditation package.

File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the "incoming.conf" file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.

File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the hosts.nntp.nolimit file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.

File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. Excessive permissions on the nnrp.access file may allow unauthorized modification which could lead to Denial of Service to authorized users or provide access to unauthorized users.

Extended ACLs may provide excessive permissions on the /etc/news/passwd.nntp file, which may permit unauthorized access or modification to the NNTP configuration.

If critical system files do not have a privileged group-owner, system integrity could be compromised.

Due to numerous security vulnerabilities existing within NIS, it must not be used. Possible alternative directory services are NIS+ and LDAP.

Adding host-based intrusion detection tools can provide the capability to automatically take actions in response to malicious behavior, which can provide additional agility in reacting to network threats. These tools also often include a reporting capability to provide network awareness of system, which may not otherwise exist in an organization's systems management regime.

Verification using the system package management tool can be used to determine that system software has not been tampered with.

This requirement is not applicable to systems not using package management tools.

Extended attributes in file systems are used to contain arbitrary data and file metadata with security implications.

Access control programs (such as TCP_WRAPPERS) provide the ability to enhance system security posture.

If the system's access control program is not configured with appropriate rules for allowing and denying access to system network resources, services may be accessible to unauthorized hosts.

Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials.

The DCCP is a proposed transport layer protocol. This protocol is not yet widely used. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the system to dynamically load a protocol handler by opening a socket using the protocol.

The RDS protocol is a relatively new protocol developed by Oracle for communication between the nodes of a cluster. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the system to dynamically load a protocol handler by opening a socket using the protocol.

Bluetooth is a Personal Area Network (PAN) technology. Binding this protocol to the network stack increases the attack surface of the host. Unprivileged local processes may be able to cause the kernel to dynamically load a protocol handler by opening a socket using the protocol.

Teredo is an IPv6 transition mechanism involving tunneling IPv6 packets encapsulated in IPv4 packets. Unauthorized tunneling may circumvent network security.

DHCP allows for the unauthenticated configuration of network parameters on the system by exchanging information with a DHCP server.

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

Responding to broadcast ICMP echo requests facilitates network mapping and provides a vector for amplification attacks.

LDAP can be used to provide user authentication and account information, which are vital to system security. Communication between an LDAP server and a host using LDAP requires protection.

The NSS LDAP service provides user mappings which are a vital component of system security. Communication between an LDAP server and a host using LDAP for NSS require authentication.

The authentication of automated LDAP connections between systems must not use passwords since more secure methods are available, such as PKI and Kerberos. Additionally, the storage of unencrypted passwords on the system is not permitted.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

LDAP can be used to provide user authentication and account information, which are vital to system security. The LDAP client configuration must be protected from unauthorized modification.

Automated file system mounting tools may provide unprivileged users with the ability to access local media and network shares. If this access is not necessary for the system's operation, it must be disabled to reduce the risk of unauthorized access to these resources.

USB is a common computer peripheral interface. USB devices may include storage devices with the potential to install malicious software on a system or exfiltrate data

A local firewall protects the system from exposing unnecessary or undocumented network services to the local enclave. If a system within the enclave is compromised, firewall protection on an individual system continues to protect it from attack.

The ability to boot from removable media is the same as being able to boot into single user, or maintenance, mode without a password. This ability could allow a malicious user to boot the system and perform changes with the potential to compromise or damage the system. It could also allow the system to be used for malicious purposes by a malicious anonymous user.

Malicious users with removable boot media can gain access to a system configured to use removable media as the boot loader.

Storing the boot loader on removable media in an insecure location could allow a malicious user to modify the systems boot instructions or boot to an insecure operating system.

If system boot loader passwords are compromised, users with console access to the system may be able to alter the system boot configuration or boot the system into single user or maintenance mode, which could result in Denial of Service or unauthorized privileged access to the system.

File system extended ACLs provide access to files beyond what is allowed by the mode numbers of the files. If extended ACLs are present on the system's boot loader configuration file(s), these files may be vulnerable to unauthorized access or modification, which could compromise the system's boot process.

The system's boot loader configuration files are critical to the integrity of the system and must be protected. Unauthorized modifications resulting from improper group ownership may compromise the boot loader configuration.

System package management tools can obtain a list of updates and patches from a package repository and make this information available to the SA for review and action. Using a package repository outside of the organization's control presents a risk of malicious packages being introduced.

The use of wireless networking can introduce many different attack vectors into the organization's network. Common attack vectors such as malicious association and ad hoc networks will allow an attacker to spoof a wireless access point (AP), allowing validated systems to connect to the malicious AP and enabling the attacker to monitor and record network traffic. These malicious APs can also serve to create a man-in-the-middle attack or be used to create a denial of service to valid network resources.