this is a very good thread!

Nats helps out a lot with this - it shows you the IP address of the signups and of the affiliates and their click trails, its a brilliant way to see fraud. I spotted a fraudulent affiliate who had 3 signups using the same IP addresses - which were registered to webservers! My suspicions were verified when I dug deeper: the surfers supposedly clicked directly to the signup pages, they never signed into the sites, they all used the same pattern for userids & passwords and the email addresses were all similar.

Plus nats also let me see all other activity on any affiliate (nats saves all info every time someone clicks an affiliate's join link, even if the surfer never signs up), you could see the exact same pattern with all other so-called surfer clicks & signup attempts.

Another huge give-away is that these webmasters tend to use epassporte and not cheque payouts.

I make it a habit to tag any affiliates who I don't know with an internal tagging system. Until I know they are not fraudulent, this tag remains on their account and any signups get extra attention. Sure it takes more time, but by being proactive and reversing these fraud charges, we avoid chargebacks and fraud payouts.