What is Firewall?
Firewall is a software that enforces the data packets will be allowed to enter or leave a network. They are into a wide variety of networked devices to filter traffic and lower risk of malicious data travelling over the public internet. Firewall is compares a type of physical barrier to limit the damage with a virtual barrier from cyber attack.
Types of Firewall
Network Level Firewall
It is the simplest firewall as it operates at the lower levels of the Open System Interconnection (OSI) reference model for networking. It is essentially kind of routes with two interface cards that filters incoming network packets. The firewall can only examine the IP address or domain name from which the packet was send and determine whether to allow or deny the traffic. The packet filtering cannot be used to grant or deny access to network on the basis of user credentials .
Circuit Level Firewall
It operates at higher level of OSI model protocol. The connection with private network are hidden from the remote user. The remote user(a user who operates hardware or software from off site location) connects with firewall and firewall forms a separate connection with the network. The result is sort of virtual circuit between the remote user and the network resource. The external user never see the IP address of internal network as user can only receive the IP address of firewall so its said to be safe configuration.
Application Level Firewall
It do not allow any packets to pass directly between the two network they connect, instead proxy application running on the firewall computer forward request to services on private network. It authenticate the credentials of a user before allowing access to the network and they use auditing and logging mechanism as part of their security policy.