A PIX firewall is a popular IP firewall that includes a network address translation appliance. It works in much the same way as an ordinary firewall by blocking attacks to the system from hackers, viruses, and worms.
It is also used to hide multiple IP addresses behind one or multiple other IP addresses. Its objective was to help solve the shortage issue of available IP addresses. The PIX has had major security flaws and in 2013 an upgrade and fix to this issue was released by the manufacturer Cisco.
The layer4 update allows for internal communication and connections, but incoming connections and communications must first be requested by a device within the system.
The PIX became the first commercially available firewall product to allow protocol specific filtering. This allows for a much tighter security setting. This also allows the PIX to be very flexible scrutiny of web-based traffic using HTTP.
The PIX can be managed and told what to do with packages that come from HTTP or any web-based point of origin. Security policies can be set up to monitor and react to instant messaging, peer-to-peer file sharing, and tunneling applications.
It can also be directed to inspect and preform deep packet inspection on applications such as FTP, ESMTP, and mobile tunneling traffic.