Internet/Intranet firewall security – policy, architecture and transaction services Written by Ray Hunt This presentation will Examines Policies that influence the design, installation and use of a firewall. It also takes a quick look at two different types of firewalls Presented by Hosein Derhamy

Content Introduction Business policies Network Service Access Policies Firewall Design Policies Firewall Architecture Packet level firewalls Application level firewalls Conclusion Question

Introduction We have seen from previous presentations that day by day as the world becomes more interconnected Network Security becomes more important. A firewall is a method of achieving security between trusted and untrusted networks The objective of the firewall policy is to minimize the organization’s zone of risk by removing the possibility of attack from an external network

Business Policy The Network Service Access Policies should extend existing business policies. The business policies that are of interest are: –Information value – what value does the management place on information –Responsibility - who is responsible for ensuring the protection of the organisation information –Commitment – what is the organisations commitment to protecting its information –Domains – what domains should or should not be protected

Network Service Access Policy(NSAP) The NSAP defines which services are to be explicitly allowed or denied between trusted and untrusted networks. The NSAP must be drafted before the firewall is implemented. It must provide a balance between protecting the trusted network from known risks while providing users with convenient access to the untrusted network.

Firewall Design Policy (FDP) FDP defines how the firewall implements restricted access and service filtering specified by the NSAP. It must take into account capabilities and limitations of the particular firewall platform as well as the threats and vulnerabilities associated with TCP/IP. Permit any service unless it is specifically disallowed Deny any service unless it is specifically permitted

Firewall Architecture One Basis for defining a firewall is the OSI 7 layer model Application Layer Presentation Layer Session Layer Transport Layer Network Layer Link Layer Physical Layer Packet level Filter Application Level Filter

Packet - level firewalls Filtering can be used to block connections to or from specific hosts or networks, as well as to block connections to specific ports Filtering based upon one of the following criteria are commonly applied –Source IP address –Destination IP address – TCP/UDP source port –TCP/UDP destination port

Example of Packet Level Filtering Internet Permits only certain connections to a network of address *.* All non telnet and non SMTP traffic blocked Telnet Gateway SMTP Gateway Firewall

Application – level firewalls Application level firewalls are more flexible, easier to configure and update. Advantages of application level firewalls or gateways are: –Information hiding –Robust authentication –Cost – effectiveness –Less - complex

Conclusion This article has examined policies that effect the design, installation and use of a firewall. The policies can be looked as a top down procedure. First come the Business policies they generate the Network Service Access Policies and then followed by the Firewall Design Policies. It is the Business Policies that require the security of the firewall.

Question Is the NSAP dependant on the type of firewall used, Why?