I've been using PrioX's AntiAFK Bot for about a month now (with Mode 1). It works great. Never been banned, but my friends has been banned, dunno if they're doing it wrong, I guess they use DND's and auto respond to whispers thingy.
No viruses, worms, trojans or keyloggers. (I use BitDefender 200
As long as you don't go with DND's or auto respond to whispers, and use the setting "respond to GM and then close WoW" you should be safe.