Avoiding brute force attacks

Hi everyone,

I keep getting warnings for brute force attempts on my server. The attempts are mainly against dovecot and exim. For example, this is just a small sample from today:


I already did the following security precautions:

1. Changed default SSH port
2. Changed default DirectAdmin port
3. Set 'SSL=1' for DirectAdmin

What is the best way to block these attempts? Please advise.

Use a firewall, search in this forum for csf firewall.

Regards