The network element must have TCP Keep-Alives enabled for TCP sessions.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-5615	NET0724	SV-5615r2_rule	ECSC-1	Low

Description
Idle TCP sessions can be susceptible to unauthorized access and hijacking attacks. By default, routers do not continually test whether a previously connected TCP endpoint is still reachable. If one end of a TCP connection idles out or terminates abnormally, the opposite end of the connection may still believe the session is available. These “orphaned” sessions use up valuable router resources and can also be hijacked by an attacker. To mitigate this risk, routers must be configured to send periodic keepalive messages to check that the remote end of a session is still connected. If the remote device fails to respond to the keepalive message, the sending router will clear the connection and free resources allocated to the session.

Description

Idle TCP sessions can be susceptible to unauthorized access and hijacking attacks. By default, routers do not continually test whether a previously connected TCP endpoint is still reachable. If one end of a TCP connection idles out or terminates abnormally, the opposite end of the connection may still believe the session is available. These “orphaned” sessions use up valuable router resources and can also be hijacked by an attacker. To mitigate this risk, routers must be configured to send periodic keepalive messages to check that the remote end of a session is still connected. If the remote device fails to respond to the keepalive message, the sending router will clear the connection and free resources allocated to the session.

STIG	Date
IPSec VPN Gateway Security Technical Implementation Guide	2013-10-08

Details

Check Text ( C-3559r4_chk )
IOS Procedure: Review the device configuration to verify the "service tcp-keepalives-in" command is configured.

Fix Text (F-5526r6_fix)
IOS Procedure: Change the configuration to include the "service tcp-keepalives-in" command.