They revert the money (if they like you), but usually if money flows one way, something else flows the other way, and they can't revert that half of the fraudulent transactions without great expenditure. Often it's not worth it and they just write it off and the whole economy bears the cost.
I'm not saying it's a better or worse plan than whatever might happen under an alternative system, but just that it's not exactly a clean solution either.
I'm not saying it's a better or worse plan than whatever might happen under an alternative system, but just that it's not exactly a clean solution either.