"We have temporarily disabled the ability to participate in Rating Battles in Pokémon X and Pokémon Y. If you try to participate in Rating Battles in your game, you should receive the following error code: 004-3003
Please continue to check the Pokémon Global Link and the official Pokémon website for updates about when Rating Battles will be available again. We apologize for the inconvenience."
It's good to see that they are taking this seriously.
If you hadn't heard there was a hack released earlier this week that allowed people to intercept incoming moves and know what the opponent had selected, as well as allowing them to see everything about your team (down to what IVs they have).