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Network Security Security-Basics
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Re: what to do?

Subject: Re: what to do?
Date: Tue, 30 Aug 2005 19:04:33 +0100
Looks to me some sort of automated script have seen this before

Could you tie down ssh access on perimeter via router to this box firewall ip 
you have one

Ips/ids would also be able to stop this assuming u wrote a signature to stop 
this that way if hacker changes ip will still stop it assuming none of these 
users are legit
 

-----Original Message-----
From: Anthony J Placilla <anthony_placilla@suth.com>
To: Bill Smith <vinet138@yahoo.com>
CC: security-basics@securityfocus.com <security-basics@securityfocus.com>
Sent: Tue Aug 30 14:33:30 2005
Subject: Re: what to do?

On Thu, 2005-08-25 at 00:30 -0700, Bill Smith wrote:
Hi Guys,

I noticed that someone is trying to hacker into my
machine. Please see below is the content of
/var/log/security.
what I would like some advice of you guys is, what
will I do with these people?
btw, I do have FW

Cheers,

Bill

Aug 24 17:56:28 tiger sshd[8229]: Invalid user golfer
from 80.68.204.50
Aug 24 17:56:28 tiger sshd[8231]: Invalid user golfer
from 80.68.204.50
Aug 24 17:56:29 tiger sshd[8233]: Invalid user golfer
from 80.68.204.50
Aug 24 17:56:30 tiger sshd[8235]: Invalid user golf
from 80.68.204.50
Aug 24 17:56:31 tiger sshd[8237]: Invalid user golf
from 80.68.204.50
Aug 24 17:56:32 tiger sshd[8239]: Invalid user goose
from 80.68.204.50
Aug 24 17:56:32 tiger sshd[8241]: Invalid user goose
from 80.68.204.50
Aug 24 17:56:33 tiger sshd[8243]: Invalid user goose
from 80.68.204.50
Aug 24 17:56:34 tiger sshd[8245]: Invalid user gorges
from 80.68.204.50
Aug 24 17:56:35 tiger sshd[8247]: Invalid user gorges
from 80.68.204.50
Aug 24 17:56:35 tiger sshd[8249]: Invalid user gorges
from 80.68.204.50
Aug 24 17:56:36 tiger sshd[8251]: Invalid user gosling
from 80.68.204.50
Aug 24 17:56:37 tiger sshd[8253]: Invalid user gosling
from 80.68.204.50
Aug 24 17:56:38 tiger sshd[8255]: Invalid user gosling
from 80.68.204.50
Aug 24 17:56:38 tiger sshd[8257]: Invalid user gouge
from 80.68.204.50
Aug 24 17:56:39 tiger sshd[8259]: Invalid user gouge
from 80.68.204.50
Aug 24 17:56:40 tiger sshd[8261]: Invalid user gouge
from 80.68.204.50
Aug 24 17:56:40 tiger sshd[8263]: Invalid user graham
from 80.68.204.50
Aug 24 17:56:41 tiger sshd[8265]: Invalid user graham
from 80.68.204.50
Aug 24 17:56:42 tiger sshd[8267]: Invalid user graham
from 80.68.204.50
Aug 24 17:56:42 tiger sshd[8269]: Invalid user grahm
from 80.68.204.50
Aug 24 17:56:43 tiger sshd[8271]: Invalid user grahm
from 80.68.204.50
Aug 24 17:56:44 tiger sshd[8273]: Invalid user grahm
from 80.68.204.50
Aug 24 17:56:44 tiger sshd[8275]: Invalid user grandpa
from 80.68.204.50
Aug 24 17:56:45 tiger sshd[8277]: Invalid user grandpa
from 80.68.204.50
Aug 24 17:56:46 tiger sshd[8279]: Invalid user grandpa
from 80.68.204.50
Aug 24 17:56:47 tiger sshd[8281]: Invalid user green
from 80.68.204.50
Aug 24 17:56:48 tiger sshd[8283]: Invalid user green
from 80.68.204.50
Aug 24 17:56:48 tiger sshd[8285]: Invalid user green
from 80.68.204.50
Aug 24 17:56:49 tiger sshd[8287]: Invalid user grey
from 80.68.204.50
Aug 24 17:56:50 tiger sshd[8289]: Invalid user grey
from 80.68.204.50
Aug 24 17:56:50 tiger sshd[8291]: Invalid user grey
from 80.68.204.50
Aug 24 17:56:51 tiger sshd[8293]: Invalid user group
from 80.68.204.50
Aug 24 17:56:52 tiger sshd[8295]: Invalid user group
from 80.68.204.50
Aug 24 17:56:52 tiger sshd[8297]: Invalid user group
from 80.68.204.50
Aug 24 17:56:53 tiger sshd[8299]: Invalid user gryphon
from 80.68.204.50
Aug 24 17:56:54 tiger sshd[8301]: Invalid user gryphon
from 80.68.204.50
Aug 24 17:56:54 tiger sshd[8303]: Invalid user gryphon
from 80.68.204.50
Aug 24 17:56:55 tiger sshd[8305]: Invalid user gucci
from 80.68.204.50


Take a look at DenyHosts
http://denyhosts.sourceforge.net/index.html

very flexible & configurable. Run out of cron at a schedule of your
choosing it will black hole the offending IPs via hosts.deny

or sshd_sentry
http://linuxmafia.com/pub/linux/security/sshd_sentry/sshd_sentry

never tried it.

IPtables can also be used. Netfilter has a "recent" module that can be
implemented something like this: (watch out for the line wraps)

-A PREROUTING -m tcp -p tcp -d $EXTERNAL --dport 22 -m recent --rcheck
--hitcount 3 --seconds 600 -j LOG --log-prefix "SSH attack: "

-A PREROUTING -m tcp -p tcp -d $EXTERNAL --dport 22 -m recent --rcheck
--hitcount 3 --seconds 600 -j DROP

-A PREROUTING -m tcp -p tcp -d $EXTERNAL --dport 22 -m recent --set -j
DNAT --to-destination $INTERNAL:22

-A OUTPUT -m tcp -p tcp -d $EXTERNAL --dport 22 -j DNAT --to-destination
$INTERNAL:22

This blocks attempts for 1 minute after 3 attempts (successful or
failed, so if someone forgets their password, they may trip it as well).

-- 
Tony Placilla, RHCT
anthony_placilla@suth.com




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