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The macOS system must be configured with the SSH daemon ClientAliveInterval option set to 900 or less.


Overview

Finding ID Version Rule ID IA Controls Severity
V-252456 APPL-12-000051 SV-252456r858505_rule Medium
Description
SSH should be configured to log users out after a 15-minute interval of inactivity and to wait only 30 seconds before timing out logon attempts. Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session or an incomplete logon attempt will also free up resources committed by the managed network element.
STIG Date
Apple macOS 12 (Monterey) Security Technical Implementation Guide 2022-09-07

Details

Check Text ( C-55912r858504_chk )
If SSH is not being used, this is Not Applicable.

The SSH daemon "ClientAliveInterval" option must be set correctly. To check the idle timeout setting for SSH sessions, run the following:

/usr/bin/grep -r ^ClientAliveInterval /etc/ssh/sshd_config*

If the setting is not "900" or less, this is a finding.
If conflicting results are returned, this is a finding.
Fix Text (F-55862r816181_fix)
To ensure that "ClientAliveInterval" is set correctly, run the following command:

/usr/bin/sudo /usr/bin/sed -i.bak 's/.*ClientAliveInterval.*/ClientAliveInterval 900/' /etc/ssh/sshd_config