[CentOS] ssh attack

Mon Feb 13 22:58:27 UTC 2006
John Merritt <jmerritt at johnlyuba.mine.nu>


I get ssh connect attempts all the time, to my servers at home and at 
work. I've noticed lately they come from a certain ip address, hitting 
every 3 or 4 seconds, trying 50 or 100 different user names and 
passwords. And I get these sweeps from 2 or 3 ip addresses a day. I 
guess this is an automated attempt to guess a user/pass and break into a 

I tried to secure ssh better by putting in an AllowUsers line in 
sshd_config. Then I thought tcp wrappers and just putting in my own 
addresses in /etc/hosts.allow would be even better, until I found out 
that all mail to my email server would be rejected.

I have 2 questions. One, is there anything you can do to stop these 
attempts, other than not running ssh?

And two, do those ssh attempts every 3 or 4 seconds slow down a box, or 
put any strain on it?