A firewall in a computer network performs a role that is very similar to that of a firewall in a building. Just as a firewall made out of concrete protects one part of a building, a firewall in a network ensures that if something bad happens on one side of the firewall, computers on the other side won’t be affected.
Firewall are used when there is a need for networks of varying levels of trust to communicate with one another. For example, a firewall typically exists between a corporate network and a public network like the Internet.
All traffic from inside to outside, and vice versa, must pass through the firewall. This is achieved by physically blocking all access to the local network except via the firewall. Only authorized traffic, as defined by the local security policy, will be allowed to pass.
The firewall itself is immune to penetration. This implies the use of a hardenedsystem with a secured operating system. Trusted computer systems are suitablefor hosting a firewall and often required in government applications.
Type of firewall
*Packet filtering
*Stateful Filters
*Application layer
A firewall can only restrict connections that go through it. It cannot protec from people who can go around the firewall, for example, through a dial-up server behind the firewall. It also cannot prevent an internal intruder from hacking an internal system.
A firewall is only as secure as the operating system on which it is installed. There are many flaws present in operating systems that a firewall cannot protect against. This is why it is important to properly secure the operating system and apply the necessary security patches before installing the firewall.
Firewall
