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

[Willy Tarreau <w@1wt.eu>]

On Sat, Oct 01, 2011 at 02:29:22PM -0400, Steven Rostedt wrote:
> On Sat, 2011-10-01 at 14:13 -0400, David Miller wrote:
> > From: Steven Rostedt <rostedt@goodmis.org>
> > Date: Sat, 1 Oct 2011 14:06:41 -0400
> > 
> > > 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:
> > 
> > By running sshd on a different port, you'll avoid the login attempts
> > as well as the overhead of the successful connection attempts.
> > 
> > I haven't allowed sshd to run on port 22 in more than 10 years.
> 
> I use to do that a long time ago, but I ran into issues because of it.
> Can't remember the exact problem. Maybe it was places I went to that did
> not allow outgoing connections to non official ports. Whatever it was,
> it was annoying enough to put sshd back to 22.

443 is pretty nice for connecting from unexpected places ;-)

> I probably can go back to a non 22 port without much issue. I have added
> a bunch of personal checks to this box that gives a report every day. I
> may add more (from what was posted in this thread already). I also have
> logwatch and rkhunter running, and just added chkrootkit now.
> 
> But moving the ssh port again may be a good idea. But I like stressing
> your net filtering code ;)

BTW ipset is particularly suited for this.

Regards,
Willy