Are you sure you wiped it out properly? Just deleting doesn't help much in these cases as they about always make some kind of clones in the system. I was very busy getting rid of it some month or so ago after my cable ISP sent me two warnings my comp was sending spam in all directions and it took me about four days to get rid of it properly. This ShieldsUp test someone posted a link of here is also helpful as you need to be sure if your ports are all stealthed. Hope some experts can add their info and correct me if I'm talking bollocks, but this way worked for me. The firewall I downloaded was Kerio 4, free of charge for homes. You also need to set it up properly.
Which leads me to a question - does anyone have a list of ports with characteristics, ie what each of them is for - as some of the messages from the firewall are difficult (for me) to deal with, ie whether to deny access or not. I was promised that list by my client/student, but he hasn't delivered yet.
