Types of Firewalls

A firewall is a boundary between a workstation and its networks. It seeks to identify threats on the network and reject or allow them entry respectively. There are three types of firewalls. They both work on different levels of the Open System Interconnection (OSI ) reference models. This difference determines the reliability and performance of the firewall. The different strategies that are used by firewalls all seek to identify and eliminate internal and external threats. There are three types of firewalls (Newman, 2003).

The screening router or the packet filters are a first generation firewall and are built on network routers. It operated on the first three levels of the OSI reference model. It uses a set of pre-configured rules to identify matches and then drops or rejects a packet accordingly. The main limitation of this firewall type is the point that no information on the connection state is assessed. Instead, low-level information on the packet is assessed like protocol types, source or destination address, and port numbers (Hare, Siyan & others, 1996).

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Stateful filters introduce a technology of stateful filtering. They do as much as the packet filters but go an extra level on the OSI reference model. They, therefore, operate up to level four. This method works by retaining packets until there is enough information to determine if they are a part of an existing connection, part of a new connection or belong to no connection. Though it also uses static rules, the fact that it introduces a connection aspect improves its efficiency (“Firewalls Explained: A Technical Support Overview“, n.d.).

Finally, there is an application level filtering. This form of filtering operates on all levels of the OSI reference model. It works by assessing both the IP addresses and the application information contained in the packets. This method works by creating multiple proxies on one firewall for various applications. It assesses the data or connection of the packets based on tailored rules for different applications. Because they are application aware, they are able to handle more complex proxies (Newman, 2003).


Firewalls Explained: A Technical Support Overview. (n.d.). Retrieved June 30, 2014, from http://www.midwestdatarecovery.com/firewalls-explained.html

Newman, D. (2003, November 7). Types of Firewall Filtering Technologies | Basics of the PIX Firewall | Pearson IT Certification. Retrieved June 30, 2014, from com/articles/article.aspx?p=101741&seqNum=3″>http://www.pearsonitcertification.com/articles/article.aspx?p=101741&seqNum=3

Hare, C., Siyan, K., & others,. (1996). Internet firewalls and network security. New Riders.

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