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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-4438	WN12-SO-000048	SV-52929r2_rule	ECSC-1	Low

Description
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.

STIG	Date
Windows Server 2012 / 2012 R2 Domain Controller Security Technical Implementation Guide	2015-09-02

Details

Check Text ( C-47234r3_chk )
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)

Fix Text (F-45855r3_fix)
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.)

Fix Text (F-45855r3_fix)

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.)