They will be able to see it sometimes, when you're computer is connected to the crossfire host. And when you're all connected to the host you will be sharing your files, IE: If you shoot someone, they see your bullets hit them, even though your bullets were loaded with your effects, not theirs. When its a raw connection to the host and everybody is connected they will see it. The most they will see it is after a patch when their files are still vulnerable.