I'm not sure I would classify this as totally black hat... I can see a few ethical purposes for undetectable trojans.
As far as trojans go, subseven is hard to beat, but it's also detected by most malware scanners. You won't find much code that will do what you need without being recognized by those scanners without visiting underground sites (no, I'm not going to list any here). You might be better off going with a known trojan if you can't make your own and just obfuscating its signature (search these forums for a how-to). Either way, you're probably not going to get anywhere without a solid knowledge of coding techniques and hex editing, etc.