What is Firewall – Type of Firewall (Full Information)


Firewalls are mainly used as a means to protect an organization’s internal network from those on the outside (Internet). It is used to keep away outsiders from gaining secret information or doing damage to internal computer systems of the organization. Firewalls are also used to limit the access of individuals on the internal network.

Types of Firewalls

Here we will talk about some different type of Firewalls-

  • Packet Filtering 

In a packet filtering firewall, data is forwarded based on a set of firewall rules. This Firewall works at the network level. Packets are filtered by type, source address, destination address, and port information. These rules are similar to the routing rules explained in the earlier section and may be thought  of as a set of instructions similar to a case statement or if statement. This type of Firewall is fast, but cannot allow access to a particular user since there is no way to identify the user except by using the IP address of the user’s computer, which may be an unreliable method. Also the user does not need to configure any software to use a packet filtering Firewall such as setting a web browser to use a Proxy for access to the web. The user may be unaware of the Firewall. This means the firewall is transparent to the client.

  • Circuit Level Relay

A circuit level relay Firewall is also transparent to the client. It listens on a port such as port 80 for http requests and redirects the request to a Proxy server running on the machine. Basically, the redirect function is set up using ipchains  and then, The Proxy filters the package at the port that received the redirect. SOCKS is an example of this type of Firewall. This type of proxy is not aware of Applications but just cross links your connects to another one outside connection. It can log activity, but not as detailed as an application proxy. It only works with TCP connections, and doesn’t provide for user authentication.

  • Application Proxy Gateway

The users connect to the outside using the proxy. The proxy gets the information and returns it to the user and can record everything that is done. This type of proxy may require a user and can record everything that is done. This type of Proxy may require a user login to use it. Rules may be set to allow some functions of an application to be done and other functions denied. The ‘get’ function may be allowed in the FTP application, but the ‘put’ function may not.

Proxy servers can be used to perform the following functions.

  1. Control outbound connections and data.
  2. Monitor outbound connections and data
  3. Cache requested data which can increase system bandwidth performance and decrease the time it takes for other users to read the same data.

Application proxy servers can perform the following additional functions-

  1. Provide for user authentication.
  2. Allow and deny application specific functions.
  3. Apply stronger authentication mechanisms to some applications.


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