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.
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: 1. CCE-35469-6