Hello ,

I suspect our server has been exploit by spammers.I believe the spammer has place a script on the server and executed it ... How do I detect out the spammer as the header of the subject, To and From always change....

I have tried executed the find command but was not able to get anything ..

I am using Linux 7.3 with Exim as the mail server...is there any spamguard that can be installed on the server to scan ?

thanks,

Are you sure it is a spammer script on your machine? Do not you happen to have an open mail relay instead? It would be more likely.

If you suspect that someone has placed scripts/programs/data on your server and is able to execute them, then you should take that server offline until it can be cleaned and fixed.

That's very unlikely in my opinion. Spam comes from open relays, not scripts.

It's not very unlikely. There's a guest column on SecurityFocus from last week detailing how a spammer used an automated script to breakin to a Red Hat box and use it as a spam zombie. The exploit was very advanced. You can find the article linked (currently the last item on the page) in the "links" section of my site http://www.amaunetsgothique.com/chort/email-sec/

As for what to do about it, run tcpdump ... should be something like this:
# tcpdump -nXttt dst port 25

See what you come up with. If you have a graphical interface (i.e. X) on your machine, then you can use Ethereal to sniff the traffic. When you see a tcp stream going to port 25 on some foreign IP, you can right click on any of the packets and do "decode tcp stream". That will show you the entire transaction, including the helo, mail from, and the body of the message.

Also, check in the links section of my site, near the top there is a link to MAPS TSI anti-relay. It has instructions for making sure your MTA (Exim) is not an open relay). My site has many tips on fighting spam (about 50% of the "threats" section has been filled out so far). If you're looking to do it for free, then you're going to want to look into SpamAssassin and setting up some RBL look-ups.

hello,

i tried with ur website but was not able to get the link...

Could you tell us what led you to believe that your system is being used to send spam. While it may not seem like such a big deal, you could potentially be mailing millions of unsolicited emails per day, so those of us who have to wade through a river of spam in our inboxes have a vested interest in seeing it stopped.

Please provide any relevent log entries from (/var/log/mesages, /var/log/maillog, etc) so we have a better idea of how to proceed. If you think that it's a script, then give us a list of running processes that seem out of the ordinary to you (especially anything that is consuming lots of resources (use the top command)). Right now you haven't really told us why you think it's a unauthorized script that was run by a cracker as opposed to just having a miss-configured mailserver that allows open relaying.

Sorry about that, what error are you getting? I'm showing outside traffic hitting it so I do not believe it's a firewall problem and I haven't changed DNS in weeks. Could you be a bit more specific, please?