I was supposed to help customers hook up modems and reboot their routers, I wasn't really supposed to dig into this stuff (and when I did I'd usually get an annoyed manager asking me to focus on my job). It would've been a great learning experience, but nobody really knew much other than that some device on the customer network was interacting with some known C&C servers.
The customer wasn't particularly interested in finding out either, they blamed us for false reports the moment their XP machine was scanned and found no viruses.
I wonder if it was a misbehaving app or had persistent root.