Title

The system is configured to allow SYN attacks. (Cat III impact)

Discussion

Adjusts retransmission of TCP SYN-ACKs. When enabled, connection responses time out more quickly in the event of a SYN DoS attack.

Check Content

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: (SynAttackProtect) Syn attack protection level (protects against DoS)” is not set to “Connections time out sooner if a SYN attack is detected”, 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: SynAttackProtect Value Type: REG_DWORD Value: 1

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> “MSS: (SynAttackProtect) Syn attack protection level (protects against DoS)” to “Connections time out sooner if a SYN attack is detected”.

Additional Identifiers

Rule ID: SV-4117r1_rule

Vulnerability ID: V-4117

Group Title: SYN Attack Protection

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.