I'm fairly sure that ones I found were either from a member here that attended the event in Japan and saved the data from the download, or that I got them off of the GTS.
Looking back on them, they might be hacked overall, but every hack-check I put them through came out pretty legit.
Mind you, a totally hacked Pokémon done correctly will look the exact same as a legit, perfect stat caught Pokémon, so really, it doesn't matter.