The Stepforth blog notes that the IAB has finalized guidelines related to Click Fraud at:
http://www.stepforth.com/blog/click-fraud-guidelines-finalized.php

Here's the post:

Click Fraud Measurement Guidelines Finalized by IAB
May 12th, 2009

Today the Internet Advertising Bureau (IAB) released version 1.0 of the guidelines for measuring click fraud
(http://www.iab.net/media/file/click-measurement-guidelines2009.pdf).