Update – Spam + Attachment filtering

Sent 3/12/2004

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Just a quick note at the end of the week to let you know about how the additional configurations on spam and attachments have been working out.

This morning we added (and replaced) some additional “black-hole” lists that our server checks against to identify known sources of spam. These lists are:

http://www.spamhaus.org
http://www.spamcop.net
http://dsbl.org/main
spamsources.fabel.dk
http://www.ahbl.org
http://www.njabl.org
http://cbl.abuseat.org

After comparing the address of the server sending email to us against the lists maintained at the above organizations our server checks the mail to validate both the mail server that is sending the message and that the user sending the message exists on that server. If the mail fails any two of these nine tests it is deleted. For example if the sending email server is discovered on one of the lists and the user account does not exists on the sending server that would count as two fails and would cause the server to delete that piece of mail.

If it passes that initial validation it is then checked for content (words, phrases, our own white and blacklists) and formatting (typical tricks used by spammers).

Based on the amount of email NOT getting redirected to our “quarantine” folder these new changes certainly seems to be cutting down the amount of bogus mail being accepted by the mail server.

Also, in just the past nine days our server has trapped over 750 virus/worm infected files. Those are infected emails that did not get delivered to your in-box!

If you have any questions about either of these features please feel free to email back with questions or comments.

Dave Riddle
Technical Director
Summit Internet Services

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