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
---------------------------------------------------
PLUG-discuss mailing list -
PLUG-discuss@lists.plug.phoenix.az.us
To subscribe, unsubscribe, or to change you mail settings:
http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss
(text/plain)