McLean HIGHER COMPUTER NETWORKING Lesson 14 Firewalls & Filtering Comparison of Internet content filtering methods: firewalls, Internet filtering software and walled gardens. Description of how a firewall can protect a LAN with an Internet connection from outside attacks.

McLean HIGHER COMPUTER NETWORKING What You Should Know About Firewalls Firewalls A firewall checks all data packets going in and out of a network. The network manager/administrator will set the policies which state which data packets will be rejected by the firewall. A firewall can be software, hardware or a combination of both.

McLean HIGHER COMPUTER NETWORKING What You Should Know About Firewalls Firewalls can use various techniques to protect a LAN with an internet connection from outside attacks: Packet Filtering Packet Filtering – filters packets based on the IP address or domain name of the sending computer. The firewall stores an access control list which is used to validate all network traffic. Circuit Level Filtering Circuit Level Filtering – the firewall sets up a secure connection between itself and the sending computer and blocks any data from any other source. Application Filtering Application Filtering – the firewall acts as a proxy server between the LAN and the external system. Only the firewalls IP address is on the network thus external users can not access the LAN only the firewall.

McLean HIGHER COMPUTER NETWORKING What You Should Know About Content Filtering Internet Content Filtering Software Internet Filtering Software can use a variety of techniques to filter out undesirable content. Filtering type of Internet Service Filtering type of Internet Service – allows access to certain Internet services e.g. www and block access to others e.g. FTP and chat rooms. Filtering URLs Filtering URLs – software stores a database of undesirable URLs. When a user requests a URL the software checks it’s database before access is allowed or denied.

McLean HIGHER COMPUTER NETWORKING What You Should Know About Content Filtering Internet Content Filtering Software cont’d… Filtering keywords Filtering keywords – software stores a database of undesirable words. When a user requests a URL the software checks it’s database before access is allowed or denied. Filtering by content rating Filtering by content rating – web sites have a content rating which states levels of violence, sexual content and objectionable language. Walled Garden A walled garden is a restricted view of the Internet. Most ISPs provide a walled garden facility for parents to allow their children to safely browse the Internet. Some companies also set up a walled garden to prevent employees surfing the Internet while they are at work!