SilverLanayru
It's a mystery.
You can make an educated guess, but at the same time, you'll need to be mindful of its stats, EVs, IVs, etc. Using pokecheck to your advantage also helps with that.I'm not finding a hack-check thread for the 6th gen so I will ask here, is it possible to make an educated guess if a pokemon obtained through the gts is hacked/cloned or not? The pokebank raised no red flags, but I'm not sure that is very significant.
Also, this thread (used to be for 5th gen, but people have been using it for 6th gen since) is the only hack-check thread.
http://www.serebiiforums.com/showthread.php?497187-Hack-Check-Thread