Malware-infected computers are increasingly being used to perpetrate click fraud, according to a study released Thursday that found their contribution was the highest since researchers began compiling statistics on the crime.
In the third quarter of this year, 42.6 percent of fraudulent clicks were generated by computers that were part of botnets, compared with 36.9 percent the previous quarter and about 27.6 percent in the same period of 2008. The increase comes as criminals trying to profit from click fraud take advantage of new advances in malware that make the practice harder to detect.
"As the botnets get more sophisticated, they're able to perpetrate more click fraud," said Paul Pellman, CEO of Click Forensics, the advertising auditing firm that prepared the report. "They're finding new ways of being distributed, and that's reflected in the data."
The jump in botnet use over the past year comes as the overall amount of click fraud dropped, from 16 percent of all paid ads in Q3 of 2008 to 14.1 percent last quarter. That means manual forms of click fraud, in which large numbers of individuals engage in the practice, has decreased by an even larger margin. Many of those people get paid to knowingly gin the advertising results, while others are tricked into it.
The data was compiled by monitoring pay-per-click campaigns on more than 300 ad networks and on advertisers' web sites.
Click fraud attempts to siphon away the commissions advertisers pay web site operators each time an ad on one of their pages is clicked on by a legitimate visitor. Fraudsters often set up websites with little or no content and then pocket big profits when ads from Google and other providers are viewed through the process.
Automated click fraud has existed for years, but over the past few months, researchers have identified several botnets that prominently offer such capabilities. Both the web-based infection known as Gumblar and the so-called Bahama Botnet contain malware that causes infected PCs to return altered Google results. When users click on them, they are taken to a series of intermediate links before arriving at their final destination.
"It's in everyone's best interest in the online community to find and stamp out click fraud," Pellman said. "The fraudsters are trying to stay a step ahead of those efforts." ®