The Interactive Advertising Bureau (IAB) has formed an industry-wide Click Measurement Working Group to meet the challenge of online advertising click fraud.

The group's representatives include Ask.com, Google, MSN Search and Yahoo!.

The group plans to form a detailed definition of a click, allowing for a standard way to determine click fraud. It will also provide recommendations on auditing and certification standards for parties in the performance-based marketing space.

Click fraud involves individuals using scripts or manually clicking on pay-per-click advertisements for financial gain.

A company could click on advertisements to deplete its competitor's marketing budget, for instance, and a website operator could be tempted to commit click fraud to increase revenues.

Search engines have repeatedly come under fire for they way they measure and determine click fraud. Yahoo! in June paid $5m and Google last week paid $90m. Both cases settled legal claims from online advertisers alleging that the search providers had provided insufficient protection to curb click fraud.

The new group is part of a broader Global Measurement Guidelines initiative by the IAB. Started in 2004, it seeks to define standards for online traffic. The group last March released guidelines for broadband measurement, determining when a broadband video commercial is counted.