Networks of hacked computers are being used more than ever to click on advertisements, a scam known as click fraud that cheats search engines, publishers and ad networks out of revenue.
For the third quarter of the year, 42.6% of fraudulent clicks came from botnet-infected computers, according to Click Forensics, a company that produces tools to detect and filter out fraudulent clicks. The figure is the highest in four years, when Click Forensics began producing reports. For the same quarter a year ago, botnets accounted for 27.5% of bad clicks. Botnets are a powerful tool for hackers.