Firewalls Essay

850 Words4 Pages
Firewalls Undoubtedly, there are three main types of firewalls used to aid in the protection of networks, and each of these have their own advantages and disadvantages when it comes to how they offer protection. First of all, a firewall can operate as a packet filtering firewall, and is set up as either a positive filter or a negative filter, which is determined by the firewall accepting or rejecting specified conditions (Stallings, Chapter 19, 2009). Moreover, the packet filtering firewall employs a series of regulations to each inbound and outbound IP packet to determine whether the packets are forwarded or discarded, and when there is a fit to one of the guidelines, that guideline is referred to for determination on forwarding or discarding the packet (Stallings, Chapter 19, 2009). However, if no match is found to one of the guidelines, then one of the two default actions are selected, and these two defaults are referred to as “default = discard”, which states what is not specifically acceptable will be disallowed, and “default = forward”, which states what is not specifically disallowed is acceptable (Stallings, Chapter 19, 2009). In fact, another form of the packet filtering firewall is the stateful packet inspection firewall that evaluates the identical packet information as the packet filtering firewall, but adds the ability to log information concerning TCP relationships (Stallings, Chapter 19, 2009). Of course, there are still two other main types of firewalls and each of these two remaining firewalls use their own methods to protect a network. Looking further, a second main type of firewall is the application-level gateway, also called an application proxy, and functions as a relay of application-level traffic. For this method of protection, the client calls the gateway using a TCP/IP application, like Telnet or FTP, and the gateway inquires the

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