No spam!

Nigerian scam! Retail spam! After months of quantified data gathering and research on the problem, SCD software engineer Greg Woods, UCAR's email postmaster, determined that the volume and offensiveness of unsolicited junk mail (spam) being received by NCAR/UCAR employees had reached a critical mass.

Working for several weeks, he converted the UCAR mail delivery system from sendmail, a common UNIX mail transfer agent, to Postfix, a system that offers more capabilities for spam filtering. NCAR/UCAR security administrator Rich Johnson, working closely with Greg, wrote the spam filtering rules.

New anti-spam measures are now in place. Spam filtering is done by IP address using a carefully selected set of the many publicly available 'block lists' based on the Domain Name System lookup technique pioneered by the Mail Abuse Prevention System (MAPS) Realtime Blackhole List (RBL) Most of the selected block lists contain the IP addresses of misconfigured hosts that have been abused to send email spam. A smaller section of the block lists contain the Internet Protocol ( IP) addresses of known Internet email spammers and email spammer supporters. Messages from IP addresses on these selected block lists are rejected.

Spam filters are only being applied to UCAR mailing lists and invalid user addresses, not yet to mail sent to individual users at UCAR. Although it's too early to know how successful the new filters will be, after only a few days in place, they have greatly reduced the spam being sent to UCAR group aliases and the number of bounced spam to the postmaster (which averaged 100 per day) from invalid user addresses.

This fall, users will be able to decide for themselves if they want to institute spam filters on their own email accounts at UCAR. A web page will be available by which individuals can chose to turn on filtering if they decide the spam problem is worth the risk of occasionally losing valid mail.

Photo: Lynda Lester—NCAR/SCD