What are slow and fast infectors?
A fast infector infects programs not just when they are run, but also when they are simply accessed. The purpose of this type of infection is to ride on the back of anti-virus software to infect files as they are being checked. By its nature, anti-virus software (a scanner, in particular) opens each file on a disk being checked in order to determine if a virus is present. A fast infector that has not been found in memory before the scanning starts will spread itself quickly throughout the disk. A slow infector does just the opposite. A slow infector will only infect files when they are created or modified. Its purpose is to attempt to defeat integrity checking software by piggybacking on top of the process which legitimately changes a file. Because the user knows the file is being changed, they will be less likely to suspect the changes also represent an infection. By its nature (and because executable code is not usually changed) a slow infector does not spread rapidly and if the inte
