Analysis of Policy Anomalies on Distributed Network Security Setups

The use of different network security components, such as firewalls and network intrusion detection systems (NIDSs), is the dominant method to survey and guarantee the security policy in current corporate networks. On the one hand, firewalls are traditional security components which provide means to filter traffic within corporate networks, as well as to police the incoming and outcoming interaction with the Internet. On the other hand, NIDSs are complementary security components used to enhance the visibility level of the network, pointing to malicious or anomalous traffic. To properly configure both firewalls and NIDSs, it is necessary to use several sets of filtering and alerting rules. Nevertheless, the existence of anomalies between those rules, particularly in distributed multi-component scenarios, is very likely to degrade the network security policy. The discovering and removal of these anomalies is a serious and complex problem to solve. In this paper, we present a set of algorithms for such a management.