On the heels of a report by Click Forensics that said incidents of click fraud have spiked to 15.8 percent across the internet, an InfoWorld story says both ad networks and advertisers may be guilty of a lack of transparency and questionable math.   

According to Click Forensics, click fraud within pay-per-click networks, which include Google and Yahoo!, jumped from 21.9 percent in the first quarter of 2007 to 25.6 percent in the second quarter of this year. 

The Click Forensics study accused Yahoo of doing little to combat click fraud. However, officials at Yahoo dispute that charge, calling vigilance against click fraud a "top priority."

"Yahoo is also actively pursuing numerous new quality initiatives that provide advertisers with more control over and visibility into the quality of their traffic," said Reggie Davis, VP of marketplace quality. "We've recently launched new features and functionality for advertisers, like quality-based pricing and enhanced geo-targeting tools, and we plan to introduce additional controls like domain blocking in the coming months."

Davis also said that between 12 and 15 percent of the traffic on Yahoo is identified as click fraud, but that advertisers are not billed for those clicks.

Google also questioned some of the math in the report.

"This estimate counts clicks Google does not charge to advertisers as fraudulent, so it is not actually a click-fraud estimate," Google said in the statement. "It is also worth noting that in all of 2007, only two advertisers have contacted us regarding click fraud data from Click Forensics, and in both cases, we found that the suspicious activity was not charged-for in the first place."

While Click Forensics stands by its numbers and Google and Yahoo have each questioned the methodology of the study, a report in paidContent.org suggests that both advertisers and ad networks could do much to improve in the fight against click fraud.

Ben Edelman, an assistant professor at Harvard Business School, said both sides need to work harder to increase transparency in the process. Edelman also added that ad networks might consider hosting message boards where advertisers could post their complaints.