What...the...F...?

It all started when I noticed that Safari, the browser I use on my work laptop, was starting to act goofy. When I typed text for any length of time it would suddenly start running really slowly even when the Windows Task Manager said I was using hardly any of my available processor power and memory and the hard drive was quiet. The last straw was when it unexpectedly froze up on me twice in one day, both times when I was halfway through a new Wikipedia entry (i.e. all of it lost). Something was definitely up.

Mindful of Snabulus' recent infection troubles, I did a full virus scan, which came up clean, but that was also something of a dilemma. All computers connected to the LAN at work are obliged to use Trend Microsystem's Virus Buster, installed from and controlled by the server. (When I first connected to the network and registered, it automatically uninstalled AVG on my machine before inserting itself.) The problem was that Snabulus discovered that Virus Buster, for all its size, expense, and hype, proved the least effective when tested along with several other virus scanners on his impacted machine. Since it is a well-known product, it seems to be easily defeated by virus writers. That led me to take a cue from Snabulus' experience and try something different. I proceeded to download and install a free virus scanner available on the internet. (I won't say which one since it's a work rather than home computer, i.e. I'm not really supposed to use it.) I then ran an initial scan, and voila!

Two Trojan horse viruses found on my C drive, both of a lesser-known type that has mainly been seen in Japan and Germany.

I'm totally puzzled as to how they got there. Since it's my work laptop, I don't really websurf with it, sticking mainly to certain, trusted sites. The only e-mail messages I've accessed with it have come from people and locations I know well, and the only attachments I'm aware of were all official documents (and it has been a long time since the last one arrived). The only other possibility I can think of was that it arrived via an infected flash drive, since I had to use a couple to check students' work. At any rate, something got on my machine and downloaded things into it that I didn't want.

The free virus scanner removed the files without any problem. There also don't seem to be any suspicious entries in my running processes list. I haven't yet looked at my registry, so I don't know what evils might be lurking there. I hope that the problem is solved, but I can't be sure. How can I deal with a problem when I don't know how it got there in the first place? Especially when this particular virus is a bit more obscure and thus doesn't have much information available? At any rate, Safari is working properly now, and I've noticed that Virus Buster has gone back to conducting lengthy scans on bootup, something I'm surprised I didn't notice wasn't happening. (Maybe I was just happy that bootup time had been magically reduced to under fifteen minutes and therefore didn't look a gift horse in the mouth. My bad, I guess.)

Curiouser and curiouser.