Inside Iowa State

July 14, 2004

Junk mail down by one million in a week

by Diana Pounds

The early numbers in Iowa State's latest skirmish with spammers are impressive. In the first week after a new spam-squashing technique began, nearly one million pieces of suspected spam were turned away from Iowa State mailboxes.

That's about a 40 percent reduction in the e-mail that normally would arrive on campus during a week's time, said Kent Ziebell, systems analyst in Academic Information Technologies.

The new spam tactic went into effect at Iowa State at 7:30 a.m. July 13. The technique is known as "greylisting" and has been used at Texas A&M with great success, Ziebell said.

The technique works like this. An e-mail from outside the iastate.edu domain arrives at an Iowa State mail server. The server refuses delivery, leaving the message on the original mail server. A legitimate mail server will try again within a short period to resend the mail, and on the second try, the Iowa State mail server will complete the delivery. However, if the original mail server is a spamming machine, it's much less likely to be set up to resend the spam.

The technique doesn't delay the delivery of legitimate mail for long, Ziebell said. Mail servers generally are set up to resend failed deliveries within a few minutes. And Iowa State's mail servers will provide speedier delivery if the volume of spam decreases.

Despite success in this latest attack on spam, ISU officials know the battle is far from won.

"It's an arms race," said Solution Center manager Frank Poduska, "and while we've gotten a step ahead, eventually spammers will catch up. Some already have e-mail systems that respond correctly to the initial refusal of mail and others eventually will upgrade their systems."

More information on greylisting and fighting spam is available at http://www.ait.iastate.edu/showitem.php?id=166

"It's an arms race and while we've gotten a step ahead, eventually spammers will catch up."

Solution Center manager Frank Poduska