So, obviously hacked pokemon are not a new thing. They've been around for a long time. But now with pokemon bank, all the hacked pokemon of older generations can be brought forward (despite that I'm sure I heard someone claim that the bank had specific ways to detect such...). Or maybe hacks have been found out for the new games too by now.
Before Y, I didn't even care to examine traded pokemon at all. I wasn't into breeding, it was just to fill pokedex. And really, even now I don't care about breeding aside from some OCDness. I'm never going to 'compete'. But, entirely not coincidentally I suspect, as soon as the bank came out (and since I was now paying attention) I started noticing the hacks. Here's my stories:
First, it turns out I myself ported a hacked pokemon up from Pearl. I've already forgotten what it was, but since I was checking all the ported pokemon's IVs, it immediately stood out: all IVs the same, but not maximum and in a master ball. Pretty much the obvious standard for hacked pokemon.
The second turned up a short while later while I was wondertrading a bunch of leftovers from breeding. This one was a Mightyena, similarly equal but not maxed IVs, master ball and also just to finish the picture, level 100.
And then we come to maybe the most hacked of all... I was sticking some decently IVed pokemon in the GTS and asking for legendaries (as you do), and I've now got:
A level 1, shiney, all max IVs, pokerus, masterball Dialga.
So... good going on that hack protection I guess heh.