topic Re: Skatter load email spam in Operating System - Linux

Skatter load email spam

Vernon Brown_4 — Thu, 12 Feb 2004 00:53:09 GMT

I'm getting email spam addressed to xxx.myserver.com where xxx equals a simple name like ann, or joe, or bin etc, and myserver is my email server's domain name. Most of the names are not valid users, but some of the names eventually match a valid user.

Now I'm starting to get "email rejected" emails from upstream email servers indicating that emails from these non-existant users was rejected due to various things, among them "file size overflow" etc.

So now the puzzle is:

How does a none user get email relayed when I have relay turned off for anybody who is not a valid user from the local net.

I have set up a virual user named Trash; I have made aliases for each of the email attempts I see coming in directing them to the valid user "trash". Question: Is it better to collect the trash this way or is it better to simply let the "User Unknown" reject happen ???

Thanks for any thoughts or experience !!

Re: Skatter load email spam

Steven E. Protter — Thu, 12 Feb 2004 01:14:11 GMT

Your best bet for a quick drop in incoming spam is to start rejecting mail by not hitting the right name.

To do this you cut down aliases to the bare minimum you need to run your system/domain whatever it is you are doing.

I still get rejects on steven.protter@investmenttool.com in my logs a year after turning it off. It gives me warm feeling inside.

I have an account called spam.

I forward all spam to it and use the scripts I gave you in your other thread to process every IP address in the spam account into access database so they can't email any more.

I'm attaching a copy of the script again.

SEP

Re: Skatter load email spam

Vernon Brown_4 — Thu, 12 Feb 2004 09:33:54 GMT

Thanks for your response Steven; I'm using your scripts, modified for my environment. Works great !!

Now I'm pondering whether I should collect the spam addressed to non users or reject it as user unknown. If someone were fishing for valid users they could use the user-unknown rejects to polish their list until it contained only valid users.

But after rejecting unknown users for about a week, I didn't see any change in the user-names they tried. Same names; same sequence.

I'll keep working on it.

Re: Skatter load email spam

Jerome Henry — Thu, 12 Feb 2004 09:42:45 GMT

Can be that this time the spam is a robot, not taking into consideration your domain name or users, or an automated worm like mydoom.
But next time ? The less information you give back, the better.
AFAIK

J

Re: Skatter load email spam

Vernon Brown_4 — Thu, 12 Feb 2004 12:34:58 GMT

I'm thinking that I might try adding to my aliases the spam names and point them back to domains that they come from. Has anyone tried that ??

Re: Skatter load email spam

Steven E. Protter — Thu, 12 Feb 2004 12:49:26 GMT

Yes, you should configure all incoming mail that does not have a valid user on your system to bounce with a User unknown.

with proper entries in:

/etc/aliases
/etc/mail/genericstable # no @domainname
/etc/mail/virtusertable # no @domainname

This should be automatic.

Still btw working on the aol problem. I have a whitelist script that detects port 25 violations and puts the user on temporary hold while I research whether or not they should go on the permanent hold list.

I'll post that system up when its ready, though it requires enhanced iptables firewall logging.

SEP

Re: Skatter load email spam

K.C. Chan — Fri, 13 Feb 2004 22:50:29 GMT

Have you try spamassassin. I am using and it works great. Herre's the url: http://spamassassin.org

Re: Skatter load email spam

Vernon Brown_4 — Fri, 13 Feb 2004 23:49:30 GMT

I downloaded SpamAssassin and will try to get it going tonight.

So far the make went well.

Thanks !!