According to Bruce Schneier there is a pretty wicked and troublesome worm/trojan/virus on the lose (and has been for the past year) called “Storm”
Normally I don’t pay much attention to these kind of things but this particular beast seems especially dangerous. As Bruce is a recognized security expert I figure he probably isn’t just crying wolf here.
Worms like Storm are written by hackers looking for profit, and they’re different. These worms spread more subtly, without making noise. Symptoms don’t appear immediately, and an infected computer can sit dormant for a long time. If it were a disease, it would be more like syphilis, whose symptoms may be mild or disappear altogether, but which will eventually come back years later and eat your brain.
You may want to read about it and check it out.