Policy Evolution with Grammatical Evolution ⋆ Yow Tzu Lim 1 , Pau Chen Cheng 2 , John Andrew Clark 1 , and Pankaj Rohatgi 2 1 Department of Computer Science, University of York, UK {yowtzu,jac}@cs.york.ac.uk 2 Department of Security and Privacy, IBM T J Watson Research Center, USA {pau,rohatgi}@us.ibm.com Abstract. Security policies are becoming more sophisticated. Opera- tional forces will often be faced with making tricky risk decisions and policies must be flexible enough to allow appropriate actions to be facili- tated. Access requests are no longer simple subject access object matters. There is often a great deal of context to be taken into account. Most se- curity work is couched in terms of risk management, but the benefits of actions will need to be taken into account too. In some cases it may not be clear what the policy should be. People are often better at dealing with specific examples than producing general rules. In this paper we investigate the use of Grammatical Evolution (GE) to attempt to infer Fuzzy MLS policy from decision examples. This approach couches pol- icy inference as a search for a policy that is most consistent with the supplied examples set. The results show this approach is promising. 1 Introduction In computer systems, a security policy is essentially a set of rules specifying the way to secure a system for the present and the future. Forming a security policy is a challenging task: the system may be inherently complex with many potentially conflicting factors. Traditionally security policies have had a strong tendency to encode a static view of risk and how it should be managed (most typically in a pessimistic or conservative way) [1]. Such an approach will not suffice for many dynamic systems which operate in highly uncertain, inherently risky environments. In many military operations, for example, we cannot expect to predict all possible situations. Much security work is couched in terms of risk but in the real world there are benefits to be had. In military operations you may be prepared to risk a ⋆ Research was sponsored by US Army Research laboratory and the UK Ministry of Defence and was accomplished under Agreement Number W911NF–06–3–0001. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the US Army Research Laboratory, the U.S. Government, the UK Ministry of Defense, or the UK Government. The US and UK Governments are authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation hereon. X. Li et al. (Eds.): SEAL 2008, LNCS 5361, pp. 71–80, 2008. c  Springer-Verlag Berlin Heidelberg 2008