I port translate SSH and direct forward to a single box which I can use to get to the rest of my network.  I only allow  access from my home network and my company network.  I can VPN into my company if I need to get home while on the road.  I do like password authentication because I often have to call some one (like my wife or my most trusted co worker) and walk them through a connection when I need information and do not have network access.  It is easy to change a password, it is harder to fedex a thumb drive from the middle of the outback.

On my windows boxes I eliminate brute force attacks by having it lock out any account for 2 seconds after a wrong password and 15 minuets after 10 wrong passwords.  But I don’t know how to configure this on Linux? 

---

From: plug-discuss-bounces@lists.plug.phoenix.az.us [mailto:plug-discuss-bounces@lists.plug.phoenix.az.us] On Behalf Of Jon M. Hanson
Sent: Thursday, February 22, 2007 9:43 PM
To: Main PLUG discussion list
Subject: Re: Got hacked?

Darrin Chandler wrote:

On Thu, Feb 22, 2007 at 09:15:27PM -0700, Jim wrote:
 

Last night I came home from work and sat down at the computer.  I 
noticed the lights on the DSL router were blinking very rapidly.  I have 
an ftp server running on my linux box (Slackware 10.2).  So I thought 
someone might have been uploading something.
 
Ftpwho showed no users logged in.  I checked the incoming directory and 
saw nothing there.
 
Tcpdump showed me that they were sending something using ssh.
 
I used find to look for anything they might have been uploading, but 
found nothing.
 
/var/log/syslog contained the following over and over for about 4 hours 
before I got home
 
Feb 22 20:43:56 ladmo smbd[6375]: [2007/02/22 20:43:56, 0] 
printing/print_cups.c:cups_cache_reload(85)
Feb 22 20:43:56 ladmo smbd[6375]:   Unable to connect to CUPS server 
localhost - Connection refused
 
Then I found in /var/log/syslog this over and over
 
Feb 21 22:11:14 ladmo sshd[26255]: error: Could not get shadow 
information for NOUSER
 
I stopped sshd and edited /etc/sshd_config by adding the following:
AllowUsers root jim
AllowGroups root
 
To test the change, I tried to log into the server via ssh and using 
another account.  It wouldn't let me log in using that other account via 
ssh.
 
I also tried
find / -mmin 1200 -size +100k
and without the size option, but found nothing from the time this was 
going on.
 
After all this I tried to send an email, but sendmail wasn't working.  I 
backed up my sendmail config files, uninstalled sendmail, reinstalled it 
and restored the config files.  Sendmail worked after that.
 
Is there anything else I should do?
 

 
Look for root kits. Reinstall?
 
Stop all services that you don't actively use. For the remainder,
consider restricting them to your local network (CUPS, etc).
 
If you have a home network, consider plugging your DSL modem directly
into one PC and using that as a firewall machine. Yes, you can also use
it as a desktop if you need.
 
Is there a compelling reason you need password authentication for ssh?
It's very easy to generate public keys and use those. You can even keep
one on a thumb drive to use if you have to. Then turn OFF password
authentication (PasswordAuthentication no) in your sshd_config.
 
 

    I'm guessing they got in through some kind of guest account you have setup (but maybe didn't know about) or another common account name with a weak password. I constantly watch my system logs and several times a week I'll get a ton of attempts to try to brute force passwords to various accounts through SSH.

-- 
Jon M. Hanson (N7ZVJ)
Homepage:  http://the-hansons-az.net
Weblog:    http://the-hansons-az.net/wordpress
Jabber IM: jon@the-hansons-az.net