Spybot is a anti-spyware application and it does not detect viruses. It detects bots, spyware, malware, worms, trojans, and some rookits.
Spybot is not like... other anti-spyware products on the cybernet. Take Spyware Doctor or SAS (Superantispyware) for example. They both are similar because they have a vast database of definitions. Spybot targets specific entries.