The SSH daemon ClientAliveInterval option must be set correctly.

From Apple OS X 10.10 (Yosemite) Workstation Security Technical Implementation Guide

Associated with: CCI-001133

SV-74113r1_rule The SSH daemon ClientAliveInterval option must be set correctly.

Vulnerability discussion

SSH should be configured to log users out after a 15 minute interval of inactivity and to only wait 30 seconds before timing out login 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 login attempt will also free up resources committed by the managed network element.

Check content

The SSH daemon ClientAliveInterval option must be set correctly. To check the idle timeout setting for SSH sessions, run the following: sudo grep ^ClientAliveInterval /etc/sshd_config If the setting is not '600', this is a finding.

Fix text

In order to make sure that ClientAliveInterval is set correctly, run the following command: sudo sed -i.bak 's/.*ClientAliveInterval.*/ClientAliveInterval 600/' /etc/sshd_config

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