1. This word is overused to the point that it is frequently confusing what people are talking about. The problem is that a scanner can be either active or passive. Example: There are variations of virus scanners: background scanner Scans for viruses continuously in the background. on-access scanner Scans a file for viruses whenever it is accessed. on-demand scanner Scans the hard disk looking for viruses whenever told to by the user. From Hacking-Lexicon