I've been dealing with an inordinate amount of bogus payments, mostly people using PayPal. I am aware of services that provide an API that returns a score, but I'd like to first explore the possibility of using something open source.
Are there any solutions (language matters not) that use freely available geolocation databases (I'm interested only in country level accuracy, and it does not have to be perfect) combined with other freely available sources of information that may help determine a fraud sale? (I.e. checking IP blacklists, etc).
I could probably write something, but its not a wheel that I'm particularly interested in studying, much less re-inventing, unless I must.