Internet "zombie" attacks are more likely to come from users of America Online than any other source, and AOL and other large internet service providers serve as launching pads for most denial of service (DoS) attacks, according to a Prolexic Technologies study released Tuesday, Reuters reports. Other top sources of such attacks include T-Mobile's German-based service; Wanadoo, a French internet provider; and Comcast.

Prolexic said the report could indicate that some ISPs don't protect their customers as much as others. But an AOL spokesman said such figures merely show that AOL has a much larger user base than other, smaller ISPs that account for nearly as many attacks. "This survey is a huge victory for our members. If they're three to four times less likely to be compromised than their peers that's not a bad thing," according to AOL.

U.S.-based computers were responsible for the largest portion of DoS traffic at 18 percent, Hong Kong, Germany, Malaysia and the U.K. had higher percentages of infected computers, Prolexic said, basing its report on attacks it saw over the last six months.