In the first quarter of 2010, 17% to 29% of clicks to online ads were fraudulent, up from 15% to 25% the previous quarter, according to separate estimates by Click Forensics and Anchor Intelligence.
Fraudulent clicks can be caused by website owners and companies seeking to waste a rival's advertising budget, but the bulk are the work of cybercriminals, according to US reports.
Cybergangs put up websites carrying only online ads. They then use botnets of infected PCs to click on the ad repeatedly to trigger payments, which they collect.
The big rise in click fraud is mainly due to increased botnet activity around the world, according to a report by Anchor Intelligence.
Increased botnet activity together with other fraudulent activity such as stealing people's identities, is a warning to brands and consumers to safeguard their information, said Ken Miller, chief executive at Anchor.
"As internet usage has grown in countries lacking appropriate cybersecurity measures, more and more computers have become infected with malware and are being used as click fraud zombies", he said in a statement.
This article was first published by Computer Weekly