Virus Flood

Instead of releasing Windows viruses intermittently, many creators of worms and trojans are pumping them out with increasing frequency.

For a while new variants of one virus, called Mytob, were appearing every hour. Some viruses appear in hundreds of different guises.
If anti-virus companies could produce patches within three hours of the first appearance of a virus, outbreaks would almost disappear ... However, Mr Marx's work has found that although response times from anti-virus companies are improving it still takes them, on average, 10 hours to update scanners and produce patches for new malicious programs.
Larger companies are generally handling these attacks but the home user and I bet smaller companies are not.