  In recent years computer systems have become increasingly complex and
consequently the challenge of protecting these systems has become increasingly
difficult. Various techniques have been implemented to counteract the misuse of
computer systems in the form of firewalls, anti-virus software and intrusion
detection systems. The complexity of networks and dynamic nature of computer
systems leaves current methods with significant room for improvement. Computer
scientists have recently drawn inspiration from mechanisms found in biological
systems and, in the context of computer security, have focused on the human
immune system (HIS). The human immune system provides a high level of
protection from constant attacks. By examining the precise mechanisms of the
human immune system, it is hoped the paradigm will improve the performance of
real intrusion detection systems. This paper presents an introduction to recent
developments in the field of immunology. It discusses the incorporation of a
novel immunological paradigm, Danger Theory, and how this concept is inspiring
artificial immune systems (AIS). Applications within the context of computer
security are outlined drawing direct reference to the underlying principles of
Danger Theory and finally, the current state of intrusion detection systems is
discussed and improvements suggested.
