Paranoid much? Apparently you don't hang out on game making forums all that often, because people are uploading and downloading exe's all the time. Construct exports exes. If you want to play the games, you have to run the programs.
Any good virus scanner will catch a program that's messing with your system files. The better ones have heuristic detection to catch malicious code hiding in an executable waiting to go off. If you're really that nervous, get some decent virus protection.
Or, as they say, "the best form of protection is abstinence." You could just not play the games.
And when I do have a finished game no, I will not upload the cap. It's private. I don't want people stealing my art/resources/code or rebranding it to eBaum's World or something. I'll release my source on examples and tuts, but asking for caps only is asking too much.