Apple iOS 12 Security Technical Implementation Guide

Password strength is a measure of the effectiveness of a password in resisting guessing and brute force attacks. Passwords that contain repeating or sequential characters are significantly easier to guess than those that do not contain repeating or sequential characters. Therefore, disallowing repeating or sequential characters increases password strength and decreases risk.

SFR ID: FMT_SMF_EXT.1.1 #1b

The more attempts an adversary has to guess a password, the more likely the adversary will enter the correct password and gain access to resources on the device. Setting a limit on the number of attempts mitigates this risk. Setting the limit at 10 or less gives authorized users the ability to make a few mistakes when entering the password but still provides adequate protection against dictionary or brute force attacks on the password.

SFR ID: FMT_SMF_EXT.1.1 #2c, FIA_AFL_EXT.1.5

On Apple iOS devices, users can access the device's contact database or calendar to obtain phone numbers and other information using a human voice even when the mobile device is locked. Often this information is Personally Identifiable Information (PII), which is considered sensitive. It could also be used by an adversary to profile the user or engage in social engineering to obtain further information from other unsuspecting users. Disabling access to the contact database and calendar in these situations mitigates the risk of this attack. The AO may waive this requirement with written notice if the operational environment requires this capability.

SFR ID: FMT_SMF_EXT.1.1 #8b

Many mobile devices display notifications on the lock screen so that users can obtain relevant information in a timely manner without having to frequently unlock the phone to determine if there are new notifications. However, in many cases, these notifications can contain sensitive information. When they are available on the lock screen, an adversary can see them merely by being in close physical proximity to the device. Configuring the MOS to not send notifications to the lock screen mitigates this risk.

SFR ID: FMT_SMF_EXT.1.1 #19

Apple iOS is required to display the DoD-approved system use notification message or banner before granting access to the system that provides privacy and security notices consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Required banners help ensure that DoD can audit and monitor the activities of mobile device users without legal restriction.

System use notification messages can be displayed when individuals first access or unlock the mobile device. The banner must be implemented as a "click-through" banner at device unlock (to the extent permitted by the operating system). A "click-through" banner prevents further activity on the information system unless and until the user executes a positive action to manifest agreement by clicking on a box indicating "OK."

The approved DoD text must be used exactly as required in the KS referenced in DoDI 8500.01. For devices accommodating banners of 1300 characters, the banner text is:

You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.
By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.

For devices with severe character limitations, the banner text is:

I've read & consent to terms in IS user agreem't.

The administrator must configure the banner text exactly as written without any changes.

SFR ID: FMT_SMF_EXT.1.1 #36

Backups to remote systems (including cloud backup) can leave data vulnerable to breach on the external systems, which often offer less protection than the MOS. Where the remote backup involves a cloud-based solution, the backup capability is often used to synchronize data across multiple devices. In this case, DoD devices may synchronize DoD-sensitive information to a user's personal device or other unauthorized computers that are vulnerable to breach. Disallowing remote backup mitigates this risk.

Note: If the AO has approved the use/storage of DoD data in one or more personal (unmanaged) apps, allowing unrestricted activity by the user in downloading and installing personal (unmanaged) apps on the iOS 11 device may not be warranted due to the risk of possible loss of or unauthorized access to DoD data.

SFR ID: FMT_MOF_EXT.1.2 #40

The iCloud Keychain is an Apple iOS function that will store users' account names and passwords in iCloud and then synchronize this data among the users' Macs, iPhones, and iPads. An adversary may use any of the stored iCloud keychain passwords after unlocking one of the synchronized devices. If a user is synchronizing devices, the user must protect all of the devices to prevent unauthorized use of the passcodes. Moreover, the keychain being transmitted through the cloud opens the possibility that a well-resourced, sophisticated adversary could compromise the cloud-transmitted keychain. Not allowing the iCloud Keychain feature mitigates the risk of the encrypted set of passwords being compromised when transmitted through the cloud or synchronized across multiple devices.

Note: If the AO has approved the use/storage of DoD data in one or more personal (unmanaged) apps, allowing unrestricted activity by the user in downloading and installing personal (unmanaged) apps on the iOS 11 device may not be warranted due to the risk of possible loss of or unauthorized access to DoD data.

SFR ID: FMT_MOF_EXT.1.2 #40

When "Allow iCloud Photos" is enabled, sensitive photos will be uploaded automatically to Apple-specified servers and available on the Apple IOS devices of other users who have accepted invitations to participate in iCloud Photo Sharing. This potentially places sensitive photos on a server outside of DoD's control and potentially makes them available to non-DoD users and devices. Disabling iCloud Photo Sharing mitigates this risk.

Note: If the AO has approved the use/storage of DoD data in one or more personal (unmanaged) apps, allowing unrestricted activity by the user in downloading and installing personal (unmanaged) apps on the iOS 12 device may not be warranted due to the risk of possible loss of or unauthorized access to DoD data.

SFR ID: FMT_MOF_EXT.1.2 #40

Enterprise books may contain DoD-sensitive information. When enterprise books are backed up, they are vulnerable to attacks on the backup systems and media. Disabling the backup capability mitigates this risk. If such books are lost, accidentally deleted, or corrupted for any reason, they can be easily retrieved from the original source.

SFR ID: FMT_MOF_EXT.1.2 #40

Passwords provide a form of access control that prevents unauthorized individuals from accessing computing resources and sensitive data. Passwords may also be a source of entropy for generation of key encryption or data encryption keys. If a password is not required to access data, this data is accessible to any adversary who obtains physical possession of the device. Requiring that a password be successfully entered before the mobile device data is unencrypted mitigates this risk.

Note: MDF PP v2.0 requires a Password Authentication Factor and requires management of its length and complexity. It leaves open whether the existence of a password is subject to management. This STIGID addresses the configuration to require a password, which is critical to the cybersecurity posture of the device.

SFR ID: FIA_UAU_EXT.1.1

The AutoFill functionality in the Safari web browser allows the user to complete a form that contains sensitive information, such as PII, without previous knowledge of the information. By allowing the use of the AutoFill functionality, an adversary who learns a user's Apple iOS device passcode, or who otherwise is able to unlock the device, may be able to further breach other systems by relying on the AutoFill feature to provide information unknown to the adversary. By disabling the AutoFill functionality, the risk of an adversary gaining further information about the device's user or compromising other systems is significantly mitigated.

SFR ID: FMT_SMF_EXT.1.1 #47

Handoff permits a user of an Apple iOS device to transition user activities from one device to another. Handoff passes sufficient information between the devices to describe the activity, but app data synchronization associated with the activity is handled though iCloud, which should be disabled on a compliant Apple iOS device. If a user associates both DoD and personal devices to the same Apple ID, the user may improperly reveal information about the nature of the user's activities on an unprotected device. Disabling Handoff mitigates this risk.

SFR ID: FMT_SMF_EXT.1.1 #47

MailDrop allows users to send large attachments up to 5 GB in size via iCloud. Storing data with a non-DoD cloud provider may leave the data vulnerable to breach. Disabling non-DoD cloud services mitigates this risk.

SFR ID: FMT_SMF_EXT.1.1 #47

Required security features are not available in earlier OS versions. In addition, there may be known vulnerabilities in earlier versions.

SFR ID: FMT_SMF_EXT.1.1 #47

The Apple iOS Mail app can be configured to support multiple email accounts concurrently. These email accounts are likely to involve content of varying degrees of sensitivity (e.g., both personal and enterprise messages). To prevent the unauthorized and undetected forwarding or moving of messages from one account to another, Mail ActiveSync Exchange accounts can be configured to block such behavior. While users may still send a message from the Exchange account to another account, these transactions must involve an Exchange server, enabling audit records of the transaction, filtering of mail content, and subsequent forensic analysis.

SFR ID: FMT_SMF_EXT.1.1 #47

Apple's Family Sharing service allows Apple iOS users to create a Family Group whose members have several shared capabilities, including the ability to lock, wipe, play a sound on, or locate the Apple iOS devices of other members. Each member of the group must be invited to the group and accept that invitation. A DoD user's Apple iOS device may be inadvertently or maliciously wiped by another member of the Family Group. This poses a risk that the user could be without a mobile device for a period of time or lose sensitive information that has not been backed up to other storage media. Configuring Apple iOS devices so their associated Apple IDs are not members of Family Groups mitigates this risk.

Note: If the site uses Apple's optional Device Enrollment Program (DEP), this control is available as a supervised MDM control.

SFR ID: FMT_SMF_EXT.1.1 #47

Because Apple Watch is a personal device, it is key that any sensitive DoD data displayed on the Apple Watch not be viewable when the watch is not in the immediate possession of the user. This control ensures the Apple Watch screen locks when the user takes the watch off, thereby protecting sensitive DoD data from possible exposure.

SFR ID: FMT_SMF_EXT.1.1 #47

The iOS Photos app is unmanaged and may sync photo's with a device user's personal iCloud account. Therefore work related photos should not be taken via the iOS camera app or stored in the Photos app. A managed photo app should be used to take and manage work related photos.

SFR ID: NA

Managed apps have been approved for the handling of DoD-sensitive information. Unmanaged apps are provided for productivity and morale purposes but are not approved to handle DoD-sensitive information. Examples of unmanaged apps include apps for news services, travel guides, maps, and social networking. If a document were to be viewed in a managed app and the user had the ability to open this same document in an unmanaged app, this could lead to the compromise of sensitive DoD data. In some cases, the unmanaged apps are connected to cloud backup or social networks that would permit dissemination of DoD-sensitive information to unauthorized individuals. Not allowing data to be opened within unmanaged apps mitigates the risk of compromising sensitive data.

SFR ID: FMT_SMF_EXT.1.1 #42, FDP_ACF_EXT.1.2

Apple iOS 12 is no longer supported by Apple and therefore, may contain security vulnerabilities.

SFR ID: FMT_SMF_EXT.1.1 #47