SV-226312r852147: The system must limit how many times unacknowledged TCP data is retransmitted. | Microsoft Windows Server 2012/2012 R2 Domain Controller STIG SCAP Benchmark

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Assessment Title

Rule Text

The system must limit how many times unacknowledged TCP data is retransmitted.

Description

Discussion Text

In a SYN flood attack, the attacker sends a continuous stream of SYN packets to a server, and the server leaves the half-open connections open until it is overwhelmed and is no longer able to respond to legitimate requests.

How this relates to the STIG checklist: STIG vs SCAP benchmark.

IA Controls

NIST SP 800-53

Not mappedCCI-002385CCE-25455-7SV-52929V-4438

References

DPMS Target Microsoft Windows Server 2012-2012 R2 DC DISA DPMS Target Microsoft Windows Server 2012-2012 R2 DC 4217

Checks

OVAL

oval:mil.disa.fso.windows:var:457600 ← xccdf_mil.disa.stig_value_tcp_max_data_retransmissions_var

DISA STIG (Manual Reference)

If the following registry value does not exist or is not configured as specified, this is a finding:

Registry Hive:  HKEY_LOCAL_MACHINE
Registry Path:  \SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\

Value Name:  TcpMaxDataRetransmissions

Value Type:  REG_DWORD
Value:  3 (or less)

SCC Automation Reference

The reconstructed evaluation script behind this rule's OVAL check(s) — every module a compound check combines, with this rule's own concrete values and DISA's SCC tool's real per-module mechanism curated from static teardown of SCC releases.

# Windows PowerShell
# Reconstructed from oval:mil.disa.fso.windows:def:4576
# The system must limit how many times unacknowledged TCP data is retransmitted.
# Per-module read mechanism curated from static teardown of DISA's SCC tool
# (SCAP Compliance Checker) -- see the SCC Automation Reference above.

# Verifies 'MSS: (TcpMaxDataRetransmissions) How many times unacknowledged data is retransmitted (3 recommended, 5 is the default)' is set to 3 or less
# registry_object (registry_test)
function test_1 {
  return (((@{String='reg_sz';ExpandString='reg_expand_sz';Binary='reg_binary';DWord='reg_dword';MultiString='reg_multi_sz';QWord='reg_qword';None='reg_none'}[(Get-Item -Path 'Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters').GetValueKind('TcpMaxDataRetransmissions').ToString()]) -eq 'reg_dword') -and (((Get-ItemProperty -Path 'Registry::HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters' -Name 'TcpMaxDataRetransmissions' -ErrorAction SilentlyContinue) | Select-Object -ExpandProperty 'TcpMaxDataRetransmissions') -le 3))
}

if (test_1) {
  Write-Output "PASS"
} else {
  Write-Output "FAIL"
}

Assessment Script Powered by AISyntax-verified

A standalone PowerShell script to assess this control automatically. Review before running it in your environment.

Syntax-checked as valid PowerShell. Not executed here — running it for real needs the actual ms_windows_2012_and_2012_r2_dc target this check assesses.

# OVAL Definition: oval:mil.disa.fso.windows:def:4576
$compliance = Test-Path -Path "HKLM:\System\CurrentControlSet\Services\Tcpip\Parameters\TcpMaxDataRetransmissions" -ErrorAction SilentlyContinue
if ($compliance) { $value = Get-ItemProperty -Path "HKLM:\System\CurrentControlSet\Services\Tcpip\Parameters\TcpMaxDataRetransmissions" -Name TcpMaxDataRetransmissions -ErrorAction SilentlyContinue }.  if ($value -and $value.TcpMaxDataRetransmissions -le 3) { Write-Output "PASS"; Exit 0 } else { Write-Output "FAIL"; Exit 1 }

Remediation

Configure the policy value for Computer Configuration >> Windows Settings >> Security Settings >> Local Policies >> Security Options >> "MSS: (TcpMaxDataRetransmissions) How many times unacknowledged data is retransmitted (3 recommended, 5 is default)" to "3" or less.   

(See "Updating the Windows Security Options File" in the STIG Overview document if MSS settings are not visible in the system's policy tools.)