E-mail security provider Postini last week said it has been awarded a patent covering its approach to identifying threat patterns in IP traffic, underlining the growing popularity of such reputation services to help block spam, viruses and other Internet-borne attacks.

The patented approach for three years has been part of Postini's e-mail security hosting service, which monitors the activity of roughly 6.5 million IP addresses, says Scott Petry, Postini founder and senior vice president of products and engineering. Now, with patent in hand, the company plans to commercialize its SMTP threat protection, making the information the service collects available to third parties such as other e-mail security companies and ISPs.

"Since we're sitting in the middle of 400 million SMTP transactions per day, we can look at things like volume, whether a sender is sending mail to a known or fake recipient, whether they've sent legitimate mail or spam," Petry says. "We're looking at data points about the type of mail a sender is trying to send, and doing analysis on it."

Postini isn't alone in using this method as an effective way to fight abuses. IronPort, CipherTrust, Symantec, Trend Micro and others include similar capabilities in their offerings. Postini's Petry wouldn't comment on whether any of the company's competitors are infringing on the recently awarded patent.

Observers say it's likely that Postini will use the new patent defensively, in case a competitor attempts to claim rights to reputation services, as opposed to actively pursuing royalties or litigation against other companies.

"It's sort of a hedge," says Matthew Prince, CEO of anti-spam consulting firm Unspam, and an attorney. "Most companies with real business models that are making money don't tend to have aggressive patent lawsuit issues. Most companies treat patents defensively."

Postini wouldn't provide a number for the patent, awarded April 15, saying it hasn't yet received the certificate from the U.S. Patent and Trademark Office. One competitor says his company will examine the patent once it's available, but doesn't believe the patent will pose problems for its business.