Inside Iowa State

July 3, 2008

New spam tactic should lighten your load

by Diana Pounds

If your e-mail box feels lighter lately, you may be reaping the benefits of the university's newest spam-fighting tactic.

University mail servers will bounce approximately 1.3 million pieces of spam this week and each week thereafter as a result of the new tactic. Jim Twetten, assistant director of Information Technology Services, said he expects much of the rejected mail will be spam that involves pornography or phishing. ("Phishing" refers to assorted e-mail scams that attempt to pry personal or financial information out of victims.)

The new spam tool piggybacks on Iowa State's Sophos PureMessage software (formerly, PerlMX). The software scans each incoming e-mail message and assigns it a "spam score." That score reflects the probability that the e-mail is spam.

Bounced at the borders

On June 16, Iowa State's mail servers began automatically bouncing all incoming mail with a 99 percent probability of being spam. Such mail is returned to the sender with a note that it was rejected.

The likelihood that any legitimate mail will be rejected is remote, says Kent Ziebell, IT senior software analyst. The PureMessage software does a very sophisticated spam analysis, he said. Anything that receives a 99 percent probability rating is almost certainly spam.

How to can even more spam

Ziebell said you can use the PureMessage system to ban even more spam from your inbox. If you're comfortable, for example, removing items with a 95 percent spam probability, or 70 percent, or even lower, you can set your mail program to dump this likely spam into the "delete" directory or, perhaps, an out-of-the-way "spam" directory. (For details, see "Coping With Spam" at www.it.iastate.edu/spam.)

Greylisting: An oldie but goodie

IT staff estimate that more than 85 percent of the e-mail attempting to get onto campus is unwanted spam, and several spam countermeasures have been in place for some time. One of the best spam-fighting techniques -- greylisting -- began four years ago. Four years is a long time by Internet standards, but greylisting continues to be effective, stopping 1 to 2 million pieces of spam per day from making it to Iowa State inboxes.

It works like this: An e-mail from the outside world arrives at an Iowa State mail server. The ISU server refuses delivery, leaving the message on the original outside mail server. Shortly thereafter, legitimate mail servers will resend and the second time around, the Iowa State mail server will complete delivery. Spamming servers are less likely to make the second effort and that accounts for a huge drop in spam at Iowa State.

Don't want to block any mail?

Twetten said faculty, staff and students who don't want to block any e-mail from their inboxes can opt to remove the spam blockers. They can remove the greylisting, the 99 percent spam blocking, or both. To opt out:

• Sign onto asw.iastate.edu with your net-ID and password.
• Click "manage user [yourNetID]"
• You'll see two e-mail options, one for greylisting and one, for e-mail spam blocking. Follow instructions to set your options.

A new spam-fighting technique should keep a million more pieces of spam out of Iowa State e-mail boxes each week.