18.4.5 Ensure 'MSS: (KeepAliveTime) How often keep-alive packets are sent in milliseconds' is set to 'Enabled: 300,000 or 5 minutes (recommended)'

Information

This value controls how often TCP attempts to verify that an idle connection is still intact by sending a keep-alive packet. If the remote computer is still reachable, it acknowledges the keep-alive packet.

The recommended state for this setting is: Enabled: 300,000 or 5 minutes (recommended).

Rationale:

An attacker who is able to connect to network applications could establish numerous connections to cause a DoS condition.

Solution

To establish the recommended configuration via GP, set the following UI path to Enabled: 300,000 or 5 minutes (recommended):

Computer Configuration\Policies\Administrative Templates\MSS (Legacy)\MSS: (KeepAliveTime) How often keep-alive packets are sent in milliseconds

Note: This Group Policy path does not exist by default. An additional Group Policy template (MSS-legacy.admx/adml) is required - it is available from this TechNet blog post: The MSS settings - Microsoft Security Guidance blog


Impact:

Keep-alive packets are not sent by default by Windows. However, some applications may configure the TCP stack flag that requests keep-alive packets. For such configurations, you can lower this value from the default setting of two hours to five minutes to disconnect inactive sessions more quickly.

Default Value:

7,200,000 milliseconds or 120 minutes.

References:

CCE-36868-8

See Also

https://workbench.cisecurity.org/files/2742

Item Details

Category: SYSTEM AND INFORMATION INTEGRITY

References: 800-53|SI-4, CSCv6|9, CSCv7|9.2, CSCv7|9.3

Plugin: Windows

Control ID: cd6132d02a82b9b7f8a1ab7411e25c4265b8f03c7c9133aa986afe0be8b9f4d4