Originally posted here by Qualm
Smart trojan users will install redundant trojans, keyloggers, etc. Then they'll keylog your passwords and steal your files, and then they'll mess with your head.
A smart trojan user would never let you know they were there so that they could continue to gain information, if there is such a thing. And even if they have many tojans installed most of them can still be removed, many AV programs have heuristics that will even find small programs that were written by the cracker themselves and not just downloaded of some geocities webpage. As for keyloggers it can be a little harder if they don't send information out, I could be wrong but I don't think that simple checking of what is typed is something that sets off alarms in most AV heuristics as many word processors do this for spell checking albeit in a slightly different way. You already installed a firewall so if you see odd connection attempts from programs that don't make sense then look into it as it could be a keylogger trying to email it's daily capture if it's set up to do that, other then that look for folders with growing text files then start looking through running processes for something out of the ordinary. I know what every process on my machine is so when something shows up I know someone's been messing with my computer.