Hey lynn,

it is possible to get rid of malware completely. I use several different programs in addition to my regular antivirus. I have used Malwarebytes antimalware on three peoples' computers to get rid of exactly what your computer got. There is a free version that is fully functional, but if you want to be able to set a schedule for it to automatically check things once a day/week/month, you need the paid version. I also use Spyhunter. That you can use to scan for free, but will need a paid version to remove things (annoying!) If you are running windows, there is also a microsoft malware thingie you can download, called windows malicious software removal tool I used to be a bit lax about such things, but having seen other computers completely locked up, and since my computer is one of the ways I earn my livelihood, I now err on the side of extreme caution.
As for where it comes from, yes, torrent sites and other popular download places are rife with this stuff. I avoid such things like the plague they are, but the tools above also run in the background and do their best to detect such things in realtime as they try to start messing things up.
Sorry you got this bug, it is very nasty indeed!