Features and Characteristics of a Firewall

1499 Words3 Pages

Firewall : A firewall is a device or software that is used to to control and filter the flow of traffic. A firewall acts as a barrier and the traffic going in each direction must pass through it. A firewall security policy is used to define that which traffic is authorized to pass in each direction. It can be designed either to operate as a filter at the level of IP packets or operate at a higher protocol layer. We can say that Firewalls are the response of a network to a host security problem but not the solution of network problems. Basic Implementation: Basically, firewalls are implemented on a network perimeter, and trusted and untrusted zones are defined for the proper functioning of a firewall. There is no need of explicit configuration in firewalls to permit the traffic from trusted zones to the untrusted zones . But the traffic from the untrusted zones to the trusted zones must be permitted explicitly. On most of the firewall systems any traffic will be implicitly denied that is not permitted explicitly from the untrusted to trusted zones (by default). There is no limitation in a firewall of only two zones, i.e. multiple ‘less trusted’ zones can present that are referred as Demilitarized Zones (DMZ’s). A security level is assigned to each firewall interface so that the trust value of each zone can be controlled, often represented as a numerical value or even a color. Example: In the above diagram, a security value of 100 is assigned to the Trusted Zone, 75 to the Less Trusted Zone and 0 to the Untrusted Zone. Generally ,the traffic from a higher security to lower security zone is allowed , whereas traffic to a higher security zone from a lower security zone requires explicit permission. Firewall... ... middle of paper ... ...t of a new connection  a part of an existing connection  or an invalid packet. 4. Circuit-Level Gateway: Another type of firewall is the circuit-level gateway also known as circuit-level proxy. A circuit-level gateway establishes two TCP connections:  one between itself and a TCP user on an inner host  one between itself and a TCP user on an outside host. Once these two connections are established, the gateway relays all the TCP segments from one connection to the other without examination of contents. It’s security function determines that which connections will be allowed. Mostly, it is used in a situation when the system administrator trusts the internal users. The gateway is configured in such a way that it is able to support application level or proxy service on inbound connections and circuit-level functions for outbound connections.

Open Document