America Online hosts more denial-of-service (DoS) spewing zombie PCs than any other ISP in the world, a report released Tuesday claimed. AOL thinks that's just fine.

Prolexic, a Florida-based company that offers a DoS mitigation service, tracked attempted attacks over the last six months to rank ISPs. AOL topped the global and U.S. domestic lists, with machines that use it as their link to the Internet accounting for 5.3 percent of DoS attacks worldwide, and 11.7 percent of those conducted in the U.S.

Worldwide, the German family of Deutsche Telekom ISPs -- and, among others -- came in second. In the U.S., Comcast, Bell South, Verizon, and Ameritech fleshed out the top five.

"We're the largest ISP on the planet," Andrew Weinstein, a spokesman for AOL, said Wednesday. "You'd expect us to have the most zombies."

Weinstein went on to say that Prolexic's numbers were actually good news for AOL. "It's a demonstration that the tools we provide are keeping members safe. Our very aggressive actions -- we provide anti-virus, anti-spyware, and firewall services to our users -- make them measurably safer than those on other ISPs."

Weinstein based that take on a comparison of Prolexic's numbers with the U.S. installed base of each ISP. Assuming JupiterResearch's estimate of AOL membership rolls is on target at 21.7 million, America Online accounts for .54 percent of the total U.S. DoS attacks for each million subscribers. Comcast, on the other hand, has just 7.4 million users, but accounted for 10.7 percent of the DoS attacks, for a rate of 1.44 percent per million. Verizon, meanwhile, posted a per million rate of 1.9 percent.

"That's three or four times as many attacks per million subscribers," Weinstein argued. "The numbers show that AOL members are significantly less likely to have been compromised by a zombie. This is actually good news for our users."

Some major U.S. ISPs were notable by their absence. EarthLink, for instance, the fourth largest provider according to JupiterResearch, was not on the list of the top 20, although Mindspring, which EarthLink acquired in 1999, came in at number 17, accounting for 1.3 percent of the DoS attacks tracked by Prolexic in the U.S.