1 Abstract This paper presents results in two mutually complementary areas: distributed immunological information assurance and a new signature matching technique based upon Kolmogorov Complexity. This paper introduces a distributed model for security based on biological paradigms of Epidemiology and Immunology. In this model each node in the network has an immune system that identifies and destroys pathogens in the incoming network traffic as well as files resident on the node. The network nodes present a collective defense to the pathogens by working symbiotically and sharing pathogen information with each other. Each node compiles a list of pathogens that are perceived as threats by using information provided from all the nodes in the network. The signatures for these pathogens are incorporated into the detector population of the immune systems to increase the probability of detection. Critical to the success of this system is the detection scheme, which should not only be accurate but also efficient. Three separate schemes for detecting pathogens are examined, namely, Contiguous string matching, Hamming Distance, and Kolmogorov Complexity. This work provides a model of the system and examines the efficiency of different detection schemes. A simulation model is built to study the sensitivity of model parameters, such as signature length, sampling rate, network topology, etc. to detection of pathogens. Index Terms Immunology, Epidemiology, Information Assurance, Kolmogorov Complexity, Signature Matching. I. INTRODUCTION Advances in computer security are emerging continuously yet, the number of computer crimes continue to rise unabated. The government, industry, and home users alike are taking serious steps to make computers and networks To appear in the Complexity Journal, vol. 9, issue 2, Nov-Dec 2003, Special Issue: "Resilient & Adaptive Defense of Computing Networks. Sanjay Goel is a professor at the University at Albany, SUNY, e-mail: goel@albany.edu . Stephen F. Bush is with the GE Global Research Center, Niskayuna, NY, 12309, USA phone: 518-387-6827; fax: 518-387-4042; e-mail: bushsf@research.ge.com. Sanjay Goel Stephen F. Bush, Senior Member, IEEE 1 Kolmogorov Complexity Estimates For Detection Of Viruses In Biologically Inspired Security Systems: A Comparison With Traditional Approaches 2