So it’s my first time setting up a VPS. Is it to be expected to ban 54 IPs over a 12h timespan? The real question for me is whether this is normal or too much.
$ sudo fail2ban-client status sshd
Status for the jail: sshd
|- Filter
| |- Currently failed: 3
| |- Total failed: 586
| `- Journal matches: _SYSTEMD_UNIT=ssh.service + _COMM=sshd
`- Actions
|- Currently banned: 51
|- Total banned: 54
`- Banned IP list: [list of IPs]
fail2ban sshd.conf
$ sudo cat /etc/fail2ban/jail.d/sshd.conf
[sshd]
enabled = true
mode = aggressive
port = ssh
backend = systemd
maxretry = 3
findtime = 600
bantime = 86400
I have disabled SSH login via password. And only allow it over an SSH key.
$ sudo sshd -T | grep -E -i 'ChallengeResponseAuthentication|PasswordAuthentication|UsePAM|PermitRootLogin'
usepam no
permitrootlogin no
passwordauthentication no
Setting the SSH service to a random high port doesn’t make security better and may make security worse. Linux has a restriction that low numbered ports require special permissions but high numbered ports do not. If an attacker manages to get low privilege code execution on your machine, they may manage to bind their service to the SSH port instead. If the server and client are configured correctly, this will cause a host key mismatch error. Continuing anyway could allow the attacker to take over your account on the server. It’s unlikely unless you are a high value target.