Well obviously, you want to look for a virus scan. If they don't, chances are they are too afraid to show it since its a fake hack.
Second: screen shots. Make sure that the screen shots are not tampered with or outdated. One main thing you want to check for is the fire mode. If you look at the bottom right hand corner, it should show the fire mode and it should NOT be incased within a box. Thats the old HUD.