[CentOS] ssh attack

[sophana]

I successfully use denyhosts that will automatically blacklist ips after 
several failed attempts.
I now have more than 70 IPs blacklisted.
John Merritt wrote:

> Hi,
>
> 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 system.
>
> 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?
>
> John
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