UCF STIG Viewer Logo
Changes are coming to https://stigviewer.com. Take our survey to help us understand your usage and how we can better serve you in the future.
Take Survey

TCP connection response retransmissions are not controlled.


Overview

Finding ID Version Rule ID IA Controls Severity
V-4437 5.097 SV-29612r1_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 no longer is able to respond to legitimate requests.
STIG Date
Windows 2003 Domain Controller Security Technical Implementation Guide 2015-06-03

Details

Check Text ( C-2235r1_chk )
Analyze the system using the Security Configuration and Analysis snap-in.
Expand the Security Configuration and Analysis tree view.
Navigate to Local Policies -> Security Options.

If the value for “MSS: (TcpMaxConnectResponseRetransmissions) SYN-ACK retransmissions when a connection is not acknowledged” is not set to “3 & 6 seconds, half-open connections dropped after 21 seconds”, “3 seconds, half-open connections dropped after 9 seconds” or “No retransmission, half-open connections dropped after 3 seconds”, then 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: TcpMaxConnectResponseRetransmissions

Value Type: REG_DWORD
Value: 2 (3 & 6 seconds), 1 (3 seconds), 0 (No retransmission)


Warning: Microsoft cautions that setting this to “No retransmission, half-open connections dropped after 3 seconds” may cause legitimate connection attempts from distant clients to fail due to time-out.
Fix Text (F-6084r1_fix)
Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “MSS: (TcpMaxConnectResponseRetransmissions) SYN-ACK retransmissions when a connection is not acknowledged” to “3 & 6 seconds, half-open connections dropped after 21 seconds”, “3 seconds, half-open connections dropped after 9 seconds” or “No retransmission, half-open connections dropped after 3 seconds”.