If you can install software on their computer that runs with their authority, yo...

		kragen on Dec 5, 2010 \| parent \| context \| favorite \| on: Cables Discuss Vast Hacking by a China That Fears ... If you can install software on their computer that runs with their authority, you can look to see what keyboard layout is configured and who their ISP is. You can also take pictures of them with their webcam and steal copies of all the passwords they type.

That seems like a pretty big if when dealing with sophisticated attackers.