Details

SSH _MUST_ be configured with an Active Server Alive Maximum Count set to 900 or less.

Setting the Active Server Alive Maximum Count to 900 (second) will log users out after a 15-minute interval of inactivity.

NOTE: /etc/ssh/ssh_config will be automatically modified to its original state following any update or major upgrade to the operating system.

Solution

Run the following bash code

/usr/bin/grep -q '^ServerAliveInterval' /etc/ssh/ssh_config && /usr/bin/sed -i.bak  's/.*ServerAliveInterval.*/ServerAliveInterval 900/' /etc/ssh/ssh_config || /bin/echo 'ServerAliveInterval 900' >> /etc/ssh/ssh_config
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Supportive Information

The following resource is also helpful.

• https://github.com/usnistgov/macos_security

This security hardening control applies to the following category of controls within NIST 800-53: Access Control, System and Communications Protection.This control applies to the following type of system Unix.

References

• 800-53|AC-12
• 800-53|SC-10
• CCE|CCE-85381-2

Source

• Tenable.com/audits