While it’s true that viruses are a nuisance, there are cases where it becomes criminal in the extreme.
The article below discusses a case where a business person was using her computer as she normally would for online banking. She had also most likely been using the computer for casual web surfing and in doing so had contracted a nasty trojan horse. The trojan horse installed software allowing the theft of passwords and other login information. The thieves then caused her computer to crash through use of software downloaded by the trojan horse. While she was dealing with the computer crash the crooks made off with her money.
Lesson learned…the computer you use for banking must be secure. You should not bank on the same computer you use to surf without making sure you surf safely. Ideally you should bank on a completely separate computer (or virtual machine) used only for banking and NEVER for surfing. For many this is just not realistic so I’ll put together a “Safe Surfing” article later…
Source: N.Y. Firm Faces Bankruptcy from $164,000 E-Banking Loss — Krebs on Security.