linux-kernel - Re: kernel.org status: hints on how to check your machine for intrusion

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Date:	Sat, 1 Oct 2011 14:06:41 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Willy Tarreau <w@....eu>
Cc:	Greg KH <greg@...ah.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel.org status: hints on how to check your machine for
 intrusion

On Sat, Oct 01, 2011 at 09:35:33AM +0200, Willy Tarreau wrote:
> 
>   - last considerations to keep in mind is that machines which receive
>     incoming connections from outside should never be able to go out, and
>     should be isolated in their own LAN. It's not hard to do at all, and
>     it massively limits the ability to bounce between systems and to steal
>     information. It also makes firewall logs much more meaningful, provided
>     they are stored on a support with limited access, of course :-)

For my machine that is connected to the outside world, I have a script
that runs every night that checks for attacks. As bots constantly look
for port 22 and 80, they find my machine without issue. When my script
detects a bunch of ssh login attempts that fail, it will add that ip
address to the iptables DROP chain:

# iptables -L -n | grep DROP | wc -l
2656

I've picked up quite a few ;)

This script only runs and scans once at night. Probably better to have
it run more often.

If any one is interested in this simple script, I can send it to them.
I'd have to audit it to make sure that it doesn't expose anything else
that may be of security to me (other machine IPs that I don't want
public, etc).

-- Steve

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