SPAM

Spam is only getting more difficult to filter. UMS currently rejects 3000-5000 e-mail everyday. We filter spam two different ways as of January 2003.

1. By domain name, IP, and e-mail address.

2. By keywords in the subject line.

When we were only blocking spam by domain name, etc., we could measure denials in the hundreds (typically 300-500 per day). Now that we filter based on the subject line AND domain name, etc., we reject thousands of messages everyday. We do this using features built in to Sendmail. It provides us with two layers of filtering spam and is very fast. Every message (inbound and outbound) is checked and if it is determined to be spam or potential spam it is rejected instantly.

If you suspect your mail is being blocked based on the subject line (we don’t block any name or address within the CU system) then you will see this in the returned message:

The e-mail system was unable to deliver the message, but did not report a specific reason. Check the address and try again. If it still fails, contact your system administrator.

< eddie.cusys.edu #5.0.0 SMTP; 553 5.0.0 SpamFilter: Rejected based on subject line.>

Please modify your subject line or contact unix_support@cusys.edu for help.

In the near future (by July 2003) we will install, configure and test “Spamassassin.” It’s a freeware tool that rates your message based on the words in the subject line. If the message scores less than a “5” it will be delivered to your mailbox with a preppended subject line. It will read “POTENTIAL SPAM:” followed by the original subject. If the message scores a 5 or higher it will be rejected.

We need your help in the war on spam. Please continue to forward any spam to abuse@cusys.edu. We will add the sender’s name and domain to our reject list. If a unique keyword exists in the subject line that is clearly related to spam language we will add that keyword to our other reject list.