1. A method comprising: parsing, by a network appliance configuration converter, network security policies of an input configuration file of a first network appliance to intermediate representations, wherein the network security policies of the input configuration file are expressed in a first language and the intermediate representations are general data structures for describing the network security policies wherein each of the intermediate representations comprises a syntax tree; optimizing, by the network appliance configuration converter, the network security policies contained in the intermediate representations by: performing an audit of security policies within the intermediate representation, wherein the audit includes one or more of: checking those of the security policies, if any, including an Internet Protocol (IP) address that is specified as ANY; checking those of the security policies, if any, including a port specified as ANY; checking those of the security policies, if any, having a range of IP addresses exceeding a pre-determined threshold; checking those of the security policies, if any, having a range of ports exceeding a pre-determined threshold; checking those of the security policies, if any, that allow access to one or more of a pre-determined set of ports of an internal network; and checking those of the security policies, if any, that allow access to one or more services of the internal network from an external network or a demilitarized zone (DMZ); and Denying access to a network if a potential leakage found in the security policies of the intermediate representations during the auditing step; converting, if the auditing step is successful, by the network appliance configuration converter, the intermediate representations to security policies of an output configuration file expressed in a second language.