How They Hide

Virus authors have developed many techniques to keep the user and any anti-virus software from detecting viruses during the infection phase.  These techniques utilize algorithms, which are the mathematical and logical expressions.  In order for a virus to continue spreading, it is pertinent that it avoid detection.  The longer a virus can exist in a computer undetected, the longer it has to replicate.

To a virus, being hard to detect is more important than being hard to remove.  Once a user knows they have a virus, they do two things.  They not only try to remove the virus, but they also attempt to prevent any of their friends or coworkers from becoming infected.  Detection, therefore, causes an abrupt end to the infection phase.

Polymorphic, stealth, TSR, and anti anti-virus are four characteristics given to viruses.  Many viruses use multiple algorithms to avoid detections.  As anti-virus software learns how to detect these algorithms, more and more algorithms are being created.