Date Added: Apr 2013
A firewall is a system acting as an interface of a network to one or more external networks. It implements the security policy of the network by deciding which packets to let through based on rules defined by the network administrator. Any error in defining the rules may compromise the system security by letting unwanted traffic pass or blocking desired traffic. Manual definition of rules often results in a set that contains conflicting, redundant or overshadowed rules, resulting in anomalies in the policy. Manually detecting and resolving these anomalies is a critical but tedious and error prone task.