Types of Firewalls
Firewall is a security device that separates trusted internal networks (internal corporate LAN) from untrusted external networks (Internet or WAN). This helps protect the organization from threats and also promotes privacy of customers.
There are different types of firewalls, each with their own distinct approach to filtering traffic. The type of firewall that you choose will depend on the specific objectives of your network and application needs.
The oldest and most commonly used type of firewall is packet filtering, which is based on the use of packets and their header information to identify problematic data. This type is implemented on routers and Layer 3 switches, allowing you to quickly block some of the most common traffic types that can lead to problems such as malware or hackers.
One of the most flexible types of firewall, stateful inspections maintain a “state table” of established connections. When new packets arrive, the firewall compares them with this state table to see if they match an existing connection. If they do, the firewall allows them through, assuming it’s safe.
A proxy firewall is as close to a physical barrier between external networks and an internal host computer as it’s possible to get. Unlike other types of firewalls, which inspect packets at the protocol level and sort them by source/destination address and port number, proxy firewalls read and understand the applications themselves, such as FTP, HTTP, DNS and other commands. This allows them to differentiate between normal or normalized applications and those that could be deemed malicious by their use of particular command sets or protocols.