Firewall

Firewall:-

          A firewall is a combination of hardware and software that sits between the internet and internal network of an organization to protect the network form outside attack.

Types of firewall:-

                      There are three main types of firewall.

(i)              Packet filter firewall

(ii)            Circuit level firewall

(iii)           Application gateway firewall.

(i)              Packet filter firewall:

It is set of rules to determine whether outgoing or incoming data packets are allowed to pass through the firewall.

(ii)            Circuit level firewall:

It is quite similar to the packet filter firewall. It also works on the basis of a set of rules for filtering packets but operates at the transport layer of the OSI Model so has greater functionality.

(iii)          Application gateway firewall:

It operates at application layer of OSI Model. It uses string user authentication to verify identity of a host attempting to connect to the network using application layer protocols such as FTP.