Computer Firewall

Learn more about computer firewall.

Firewall is referred to as a virtual barrier to unauthorized users from connecting to a computer while allowing access to authorized users. Firewalls are sometimes a set of software, but it can also be in the form of hardware installed with software defined with rules and procedures to differentiate the authorized and unauthorized computer users. Computer firewall is a very crucial tool to protect the computer from hackers and viruses, especially over Internet. To fully understand the operation of Computer firewall, we have to take a look at the technical aspects of a firewall.


  • Firewall Techniques

  • Types of firewall

Firewall Techniques

Computer firewall uses different techniques and methods to filter hackers and viruses from harming the computer.

Circuit Level Gateway uses the system of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). Both TCP and UDP are part of Internet Protocol Suite, which is a set of communication protocols such as TCP and IP having layer of pathways along which information travels from one point to another. Once a connection is established, the information flows without any external interference.

Application Gateways is another good way to connect applications such as FTP (File Transfer Protocol) and Telnet (sometimes referred to as Terminal Network). Its main purpose is to secure the connection between applications for free flow of information.

Packet Filters inspect each and every packet that passes thought the gateway. The information travels in the form of packets and it recombines when it reaches its destination. Filtering packets make the connection a little slower, but it provides an effective security.

Types of firewall

There are many types of firewalls used in different organizations depending upon the level of security. Some of the main types being used are discussed below.

Network Layer Firewall-Network Layer Firewall works at the lowest levels of the Internet Protocol Suite by reading every packet that passes through, and it allows packets to pass through if it defines its identity and matches to the set of rules that were previously defined by the administrator.

It further divides into two sub categories of stateful and stateless. Sateful firewall scans the whole session established, and it takes more time. But stateless firewall scans overall sessions, and it requires less memory and time to complete its scan.

Application Layer- Application layer scans all browser, telnet and ftp traffic. Its basic purpose is to protect the hardware from Trojans and Worms, and it restricts data without the identification of the sender. Most of the Computer Firewall works on this principle.

Network Address Firewall- Its main function is to hide the address of the host so that the suspect cannot find the location preventing it from sending infected or unauthorized data that can harm a hardware or software.

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