This part of ISO/IEC27033 gives guidance for securing communications between networks using security gateways (firewall, application firewall, Intrusion Protection System, etc.) in accordance with a documented information security policy of the security gateways, including: identifying and analysing network security threats associated with security gateways; defining network security requirements for security gateways based on threat analysis; using techniques for design and implementation to address the threats and control aspects associated with typical network scenarios; and addressing issues associated with implementing, operating, monitoring and reviewing network security gateway controls.