A filter module allows controlling network security by specifying security rules for traffic in the network and accepting or dropping communication packets according to these security rules. A set of security rules are defined in a high level form and are translated into a packet filter code. The packet...http://www.google.com.hk/patents/US5606668?utm_source=gb-gplus-share專利 US5606668 - System for securing inbound and outbound data packet flow in a computer network
