A new Pokémon X/Y online battle exploit called "Battle Analyser" is ruining online play by intercepting data. This is not good. This is not good at all.
As pointed out by NeoGAF forum member UltimateIke, here's how the exploit program works: A PC is used as a wireless hotspot to intercept online data, scanning an opponent's entire party of Pocket Monsters and even showing the moves the opponent uses in battle.
This exploit apparently affects all online battles (well, those against players you don't know or trust) and is the equivalent of seeing another player's hand in a round of poker. In short, it takes all the strategy out of the game's online component, giving cheaters a brutally unfair advantage.
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So they know all your moves, that don't mean you should be beaten.