Artificial Immune Systems: Survey and Applications in Ad Hoc Wireless Networks

This document reviews recent efforts in the area of Artificial immune systems (AIS) and their applications for (ad hoc) wireless networks. It presents basic mechanism of Human immune systems, introduces the reader to the learning paradigms of AIS, sums up misbehavior in ad hoc wireless networks and discusses pros and cons of AIS in increasing robustness of ad hoc wireless networks against misbehavior . INTRODUCTION AND MOTIVATION Ad hoc wireless networks lack a centralized authority that controls the flow of packets. Instead, each node (mobile device) in an ad hoc network 1 serves as a router. Each node is able to forward packets only to its neighbors 2, and vice-versa each node is able to receive packets only from its neighbors. Nodes are allowed to move and can be switched off and on at any time. Due to the lack of a centralized authority ad hoc networks are extremely vulnerable to user misbehavior. Sin ce nodes within an ad hoc network are expected to have limited computational power and be battery powered, a system that is going to protect them has to be lightweight. Additionally, it has to be adaptive as ad hoc networks are expected to operate autonomously with sporadic maintenance [33]. Therefor e classical intrusion detection approaches, many of which ar e based on intrusion signatures, are not suitable for this tas k. An example of systems that fulfill the above requirements are Artificial immune systems (AIS). AIS are based on a mechanism that is present in human bodies, namely, on the Human immune system (HIS) ; see [17, 22, 46, 55, 4] and references therein. AIS are a part of recent promising advances in Intrusion detection systems [39, 54, 52, 42, 14, 5, 48, 56, 38]. ARTIFICIAL IMMUNE SYSTEMS Background The Human immune system is a rather complicated mechanism that is able to protect humans against an amazing set of 1We will use ad hoc wireless network, ad hoc network, or simply just network interchangeably. 2Nodes that lie within radio range of the sending node. extraneous attacks. This system is remarkably efficient, mo st of the time, in discriminating between selfandnon-selfantigens. 3 A non-self antigen is anything that can initiate an immune response; examples are a virus, bacteria, or splinter. Th opposite to non-self antigens are self antigens; self antig e s are human organism’s own cells. The important features of HIS have often a dual nature. These dual natures include self vs non-self recognition, in nate vs acquired immunity, primary vs secondary response, or general vs specific response. Some immunity mechanisms are antigen specific, systemic (not confined to a local area), or have memory (they are able to launch a stronger response next time a specific antigen is encountered). Often are certa in phenomena explained only through hypotheses, an example is the theory of idiotypic networks by Jerne [29]; this theor y attempts to characterize the dynamics of interaction betwe n antibodies and antigens. The above mentioned mechanisms are a result of complex chemical and biological reactions within our bodies. These reactions employ different kinds of cells, proteins, or molecules. Examples are Band T-cells, macrophages, dendritic cells, killer cells, mast cells, interleukins, inte rf rons etc. These cells act in a distributed manner at various place s in a human body such as bone marrow, tonsils, thymus, adenoids, Peyer’s patches, or the appendix.