4.2.18 Ensure sshd MaxStartups is configured

Information

The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon.

To protect a system from denial of service due to a large number of pending authentication connection attempts, use the rate limiting function of MaxStartups to protect availability of sshd logins and prevent overwhelming the daemon.

Solution

Edit the /etc/ssh/sshd_config file to set the MaxStartups parameter to 10:30:60 or more restrictive:

MaxStartups 10:30:60

Note: First occurrence of a option takes precedence.

See Also

https://workbench.cisecurity.org/benchmarks/15964