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Third generation firewalls were built to filter information across all layers of the OSI model – including the application layer – allowing them to recognize and understand applications as well as some of the widely-used protocols such as File Transfer Protocol (FTP) and Hypertext Transfer Protocol (HTTP). Based on this information, the firewall can detect attacks trying to circumvent it via an allowed port or misuse of a protocol.

The latest firewalls still belong to the third generation, however they are often described as “next-generation” (or NGFW). They combine all the previously used approaches with deeper inspection of the filtered content, e.g. matching it against a detection database to identify potentially harmful traffic.

These modern firewalls often come with additional security systems built into them such as virtual private networks (VPN), intrusion prevention and detection systems (IPS/IDS), identity management, application control and web-filtering.