Is it possible for an outside user (user A) to hack into a computer
running P2P software such as Limewire (user B)? User B may be running the computer on an unsecured wireless network.

I know that there is a security flaw allowing user A to read user B's files...but what I need to know is whether user A can actually add files to user B's computer, or hack into user B's computer and cause it to appear as if user B was sending certain files, when in actuality it is user A making unauthorized use of user B's computer?

Thanks for any help