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
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 :
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.