30Nov/040
How To Defend Your Website Against Click Fraud
Michael Bloch and Dmitri Eroshenko has done a whitepaper on click fraud that you can download for free.
Or more correctly: you can leave your name and email address 
Haven't been through the report yet, but hopefully it will show up in my inbox shortly.
If you suspect somebody is deliberately using their Google AdSense account to empty your Google AdWords pockets, then you might want to read the report yourself - and Michael and Dmitri would probably also like to see you as paying customers