Firewalls Techniques

Don't forget to read firewall introduction here.

There are several types of firewall techniques:

Packet filter:
Packet filtering inspects each packet passing through the network and accepts or rejects it based on user-defined rules. Although difficult to configure, it is fairly effective and mostly transparent to its users. It is susceptible to IP spoofing.

Application gateway:
Applies security to specific applications, such as FTP and Telnet servers. This is very effective, but can impose a performance degradation.

Circuit-level gateway:
Applies security mechanisms when a TCP or UDP connection is established. Once connection made, packets can flow between the hosts without further checking.

Proxy server:
Intercepts all messages entering and leaving the network. Here the proxy server effectively hides the true network addresses.

Hardware vs Software Firewall

Hardware firewalls provide higher level of security and hence preferred for servers where security has the top most priority whereas, the software firewalls are less expensive and are most preferred in home computers and laptops.

      Hardware Firewall.

Hardware firewall providing protection to a Local Network.

      Software Firewall.

Computer running firewall software to provide protection.

Hardware firewalls usually come as an in-built unit of a router and provide maximum security as it filters each packet in the hardware level itself even before it manages to enter your computer.

Read Other Parts Of This Post :
Firewall Introduction, Firewall Techniques, Firewall Configuration