Thanks in part to armies of compromised computers, click fraud reached an all-time high in the fourth quarter.
Click fraud lets Web sites increase revenue from ads supplied by services such as Google's AdSense or the Yahoo Publisher Network, though those companies take measures to screen out bogus links so advertisers don't have to pay. But that doesn't stop people from trying, according to a new report from Click Forensics, a company that monitors for click fraud and sells detection services.
"The overall industry average click fraud rate grew to 17.1 percent for the fourth quarter of 2008. That's up from 16.0 percent in the third quarter of 2008 and from the 16.6 percent rate reported for the fourth quarter of 2007," the company said Wednesday.
Humans can click on ads, but increasingly fraudsters turn to botnets, the swarms of computers taken over through remote attacks that can do fraudsters' bidding without computer users' knowledge.
"Traffic from botnets was responsible for 31.4 percent of all click fraud traffic in the fourth quarter of 2008. That's up from the 27.6 percent rate reported for the third quarter of 2008 and the 22.0 percent rate reported for the fourth quarter of 2007," Click Forensics said.