How can someone like an exchange track the Bitfinex hacked coins to make sure the hacker cannot exchange them?
Does a service exist to make it easy for the exchange to call an API with the deposit txid and get back an answer if the input coins are tracked to the hack?
I understand that people don't like the idea of tracking bitcoins, but as an exchange if bitcoins associated with the hack are deposited on your platform and allowed to be converted into USD you are potentially liable for facilitating a crime. An exchange needs an easy way to keep track of these coins so at the very least they can put a hold on the user's account while investigating the source of the deposited coins. This happens with USD all the time, so I'm not sure why people would expect bitcoins to be any different. No exchange wants to be a party of criminal actions.
Hopefully now the question is more clear. So does such a service exist or must the exchange write their own code to handle this?