The network devices must be configured to timeout after 60 seconds or less for incomplete or broken SSH sessions.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-5612	NET1645	SV-5612r4_rule		Medium

Description
An attacker may attempt to connect to the device using SSH by guessing the authentication method, encryption algorithm, and keys. Limiting the amount of time allowed for authenticating and negotiating the SSH session reduces the window of opportunity for the malicious user attempting to make a connection to the network device.

STIG	Date
Firewall Security Technical Implementation Guide	2017-12-07

Details

Check Text ( C-3534r6_chk )
Review the configuration and verify the timeout is set for 60 seconds or less. The SSH service terminates the connection if protocol negotiation (that includes user authentication) is not complete within this timeout period. If the device is not configured to drop broken SSH sessions after 60 seconds, this is a finding.

Fix Text (F-5523r5_fix)
Configure the network devices so it will require a secure shell timeout of 60 seconds or less.