Re: howto block ssh brute-force

[TiB <repasi.tibor@chello.hu>]

Felipe Figueiredo wrote:

> Hello,
>
> once in a while (say, every two weeks) I get a brute-force
> login/password scan attempt in my server (i.e., a single ip tries
> dictionary account names and passwords at random). SSH access is
> needed by many users, and  (RSA/DSA key)-only access is, at present
> time, unwanted. So far none such attempt was lucky (to my knowlege),
> but it always gives me creeps when I see unusually big logwatch
> reports, and my contacts to sysadmins of originating networks are
> usually ignored.
>
> Any ideas?
>
> Maybe there is a way to temporarily block ips upon such attempts (is
> this a FAQ?), or maybe divert them like what portsentry does for
> portscans?
>
>
>  
I'm using to limit access from a each address to 3 connections per 
minute. It's easy to set up and works fine using iptables ipt_recent 
module.

e.g.:

## SSH flood protection
iptables -A INPUT -p tcp --dport 22 -m recent --update --seconds 60 
--hitcount 3 --rttl --name SSH -j LOG --log-prefix "SSH conn flooding "
iptables -A INPUT -p tcp --dport 22 -m recent --update --seconds 60 
--hitcount 3 --rttl --name SSH -j DROP
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --set 
--name SSH -j ACCEPT

regards,
   RT