An engineer investigating Google's click fraud detection system has concluded that the company's efforts to combat the scourge are "reasonable." Alexander Tuzhilin, a professor of information systems at NYU, laid out his findings in a report issued as part of a class-action lawsuit against the company.

Google and the plaintiffs in the Arkansas case, Lane's Gifts v. Google, have agreed to a $90 million settlement, but the court is still determining whether to approve the settlement agreement. One of the settlement terms was that a third-party expert be allowed to examine the company's detection methods.

Given Google's secrecy around its click fraud detection systems, Tuzhilin is one of the rare outsiders given the opportunity to probe the company's methods. Tuzhilin reviewed internal documents, interviewed Google personnel and received demos of various systems as he prepared the 47-page report.

Though Tuzhilin reaches the conclusion that current click-fraud efforts are "reasonable," he questions one of the company's policies before March 2005. Before that time, when an ad received a double click, one click followed by an immediate second click, advertisers were charged for both clicks.

"For me, the second click in the double click is invalid. . . and the advertisers should not be charged for it," he wrote. "It is not clear to me why it took Google so long to revise the policy of charging for double clicks. Nevertheless, this policy was revised in March 2005 despite the fact that the company lost 'noticeable' revenues by taking this action."

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