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Re: targetted SSH bruteforce attacks
From: Gary Baribault <gary () baribault net>
Date: Thu, 17 Jun 2010 11:28:04 -0400

On this system, there is only one user allowed, and that's me. On one
of my other systems, where two, but both good security guys. I run a
bash script every night to grep the successful and unsuccessful logins
every night that is mailed to me, that's how I spot these things
quick. Also Denyhosts emails me for every Deny.

Gary Baribault
Courriel: gary () baribault net
GPG Key: 0x685430d1
Signature: 9E4D 1B7C CB9F 9239 11D9 71C3 6C35 C6B7 6854 30D1

On 06/17/2010 10:56 AM, Michael Holstein wrote:

Is anyone else seeing this type of attack? Or is someone really
targeting MY box?


No, I assure you it's not just you.

It's also not uncommon to see a sequential (basically a nmap -p 22) scan
at full throttle several times a day.

You can basically :

a) move to another port (obscurity .. but pretty effective in weeding
out the casual versus committed)
b) switch to public key only auth (recommended anyway if possible).
c) use denyhosts, tarpitting, etc. to frustrate the casual guessers and

The ones that are committed will find a way around (a) and (c). But it
will take somebody a long time to properly guess a key for (b) ..
unless you forgot to patch your Debian SSHd from their little snafu ..
but you'd have been owned long ago if that was the case.

If you really must use passwords on a multi-user system listening on
tcp/22, then employ something like the PAM modules for JTR
(/pam_passwdqc) /just to make sure people don't use stupid ones.


Michael Holstein
Cleveland State University

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