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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-4438	WN08-SO-000048	SV-48127r1_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 8 / 8.1 Security Technical Implementation Guide	2015-06-16

Details

Check Text ( C-44853r1_chk )
Analyze the system using the Security Configuration and Analysis snap-in. (See "Performing Analysis with the Security Configuration and Analysis Snap-in" in the STIG Overview document.) Expand the Security Configuration and Analysis tree view. Navigate to Local Policies -> Security Options. (See "Updating the Windows Security Options File" in the STIG Overview document if MSS settings are not visible in the system's policy tools.) If the value for "MSS: (TcpMaxDataRetransmissions) How many times unacknowledged data is retransmitted (3 recommended, 5 is the default)" is not set to "3" or less, this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \System\CurrentControlSet\Services\Tcpip\Parameters\ Value Name: TcpMaxDataRetransmissions Value Type: REG_DWORD Value: 3

Check Text ( C-44853r1_chk )

Analyze the system using the Security Configuration and Analysis snap-in. (See "Performing Analysis with the Security Configuration and Analysis Snap-in" in the STIG Overview document.)
Expand the Security Configuration and Analysis tree view.
Navigate to Local Policies -> Security Options.

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

If the value for "MSS: (TcpMaxDataRetransmissions) How many times unacknowledged data is retransmitted (3 recommended, 5 is the default)" is not set to "3" or less, this is a finding.

The policy referenced configures the following registry value:

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

Value Name: TcpMaxDataRetransmissions

Value Type: REG_DWORD
Value: 3

Fix Text (F-41264r1_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 the default)" to "3" or less.