E-mail management vendor IronPort Systems Inc. said Monday it has acquired SpamCop, a public anti-spam blacklist that relies on user volunteers to develop its spam database. While financial terms of the deal weren't divulged, IronPort is investing more than $1 million in SpamCop to keep the volunteer-based model viable.

Several blacklist sites--among them OpenRBL, Monkeys.com, and Osirusoft.com--have been forced to shut down in recent months due to denial-of-service attacks by spammers, and IronPort hopes to prevent SpamCop from meeting a similar fate. The company plans to integrate SpamCop's data with its SenderBase E-mail reputation service, which collects user complaints about spam and tracks the top senders of E-mail by domain and IP address.

Patrick Peterson, general manager of information services for IronPort, says "sender reputation" data is becoming an increasingly important spam deterrent as spammers become more deceptive with their tactics, often luring users to reveal their personal information by designing their messages to appear as if they're coming from legitimate companies. Often the text of the message doesn't provide sufficient information to provide a future reference point for filters, whereas sufficient user complaints about deceptive spammers can tag the sender as unreputable. Peterson says 99% of SpamCop's value to IronPort is in the data that it uses to compile blacklists rather than in the blacklists themselves. "We don't want to run a binary black-list service," he says. "We want to provide a rich data set to ISPs, universities, and corporations."

IronPort already offers anti-spam protection by reselling Brightmail's filtering technology as a component of its family of E-mail gateway appliances. Its investment in SpamCop will enable the site's founder, Julian Haight, to hire people and ensure further innovation, build up the site's infrastructure, and strengthen its denial-of-service protection. Haight will continue to run the SpamCop site, with additional backing from IronPort.