Kate A asks: I would be interested to know how antivirus software actually works. How do they actually kill the viruses? Thank you.

Pete replies: here is a very simplistic explanation. Antivirus software works in two main ways. Firstly, it determines what kind of file it is scanning, then looks for patterns, sometimes called signatures (think of fingerprints) that have been previously identified in known viruses. Secondly, to some extent the antivirus software may apply heuristics (rules of thumb). For instance, if it has webbed feet, feathers and wings and quacks then it's probably a duck, so treat it accordingly.

Removal of an identified virus can be a simple matter of repairing the program file that the virus has infected. In the worst recent cases, removal can be hellishly difficult because the virus is deeply embedded in the bowels of the Windows operating system.