SSH server is by default configured to allow a user or client several tries to authenticate within a period before it's considered a failure. The default configuration allows three authentication attempts within 120 seconds (2 minutes), where if it still fails, the client will be given the Permission denied error and the session closed.
The SSH server will log the failed login, and the user will then be allowed to log in again after the period has passed. Temporarily blocking failed SSH login might slow down malicious login attempts but will not deter brute-force attacks by bots.
Related: How to block SSH login brute force
Related: How to show failed SSH login
$ sudo vi /etc/ssh/sshd_config [sudo] password for user:
Remove # if exist at the start of the line to uncomment.
Can also use unit such as m for minute. Set the value to 0 to disable the feature.
Add the line if it doesn't already exist and remove # at the beginning of the line if it exists.
$ sudo systemctl restart sshd
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