Firewall policies can be extremely complex and difficult to maintain, especially on networks with more than a few hundred machines. The difficulty of configuring a firewall properly often leads to serious errors in the firewall configuration or discourage system administrators from implementing restrictive policies. In previous research, we developed a technique for modeling firewall policies using Multiway Decision Diagrams and performing logical queries against a decision diagram model. Using the query logic, the system administrator can detect errors in the policy and gain a deeper understanding of the behavior of the firewall. The technique is extremely efficient and can process policies with thousands of rules in just a few seconds. While queries are a significant improvement over manual inspection of the policy for detecting that errors exist, they provide only limited assistance in repairing a broken policy. In this paper we present two extensions to our work, examples and hist...
Robert M. Marmorstein, Phil Kearns