I'm wondering what Google's methodology is for detecting fraudelent repeated clicks? I'm planning a small app that registers users' clicks and want to employ the most foolproof and efficient method for preventing repeat clicks. IP alone wouldn't work right? A combination of IP and user agent? Or cookies?
Well you are doing something which google does in a large extent .. till the extent I know , if you have a High CTR ratio and low impressions then you are in limelight and put in a category of being watched .. and if this happens for a long time then You are banned from adsense Networkkk.. along with IP you need to have CTR ratio knowledge as well.
Google does not give that information to publishers or any one else but may be they determine it when CTR increases on large Scale
you should ask why there are billion people joining the program and nobody was successful with invalid and fraudulent clicks