Title

The system must be configured to limit how often keep-alive packets are sent. (Cat III impact)

Discussion

This setting controls how often TCP sends a keep-alive packet in attempting to verify that an idle connection is still intact. A higher value could allow an attacker to cause a denial of service with numerous connections.

Check Content

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: (KeepAliveTime) How often keep-alive packets are sent in milliseconds" is not set to "300000 or 5 minutes (recommended)" or less, this is a finding. The policy referenced configures the following registry value: Registry Hive: HKEY_LOCAL_MACHINE Subkey: \System\CurrentControlSet\Services\Tcpip\Parameters\ Value Name: KeepAliveTime Value Type: REG_DWORD Value: 300000

Fix Text

Configure the policy value for Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options -> "MSS: (KeepAliveTime) How often keep-alive packets are sent in milliseconds" to "300000 or 5 minutes (recommended)" or less.

Additional Identifiers

Rule ID: SV-48125r1_rule

Vulnerability ID: V-4113

Group Title: TCP Connection Keep-Alive Time

Expert Comments

CCIs tied to check.

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