[infornography]

There are infact two "anti-cheats" for the cheat you're talking about. The first is to just be observant, and make sure someone has an allied symbol above their heads before you assume they're a friend. One of the default German skins is tan with a mask and looks like an ally, so you need to learn to do this instinctively. if that isn't satisfactory, you can do my favorite trick: force models. it's a check box on the MP option menu where you select models and it makes all allies appear as the model you selected, and all germans as the model you selected. this prevents people from disguising as the other team, and prevents them from using the invisibility trick. I find it much easier to play if all americans are dressed in tan, and all germans are dressed in black.