Overview
A firewall is a component of a computer or a network that permits authorized access while blocking unauthorized entry. It guards a network gateway to protect the resources of a private network. The firewall filters the data and enters and leaves a system or network. Other tools include data encryption and decryption, entry permission regulation, and regulating data transmission between different security systems.
A firewall inspects a packet of data based on certain "rules." This software program inspects the type of protocol and the source and destination of the host address and port. Firewalls can be configured to permit data entry from certain trusted websites and prevent entry of data packets from malicious websites.
Different types of firewalls include proxy servers, application gateways, packet filters, and circuit level gateways. A proxy server is a type of firewall through which each and every data packet should pass through before entering or exiting a system. A packet filter examines and regulates transmission of every packet of information. A circuit gateway conducts security checks during first time connections. Application gateways are used as firewalls only when certain websites need to be blocked.
Benefits
Firewalls protect computers from security threats from spam, spyware, and hackers. Firewalls prevent the entry of harmful virus programs like Trojan backdoors into your system. Firewalls also protect you from email flooding and service attacks. Firewalls prevent the entry of macros and viruses that could disable and destroy your computer system. You can even configure your firewall to filter your spam email.
How It Works
Firewalls work with built in filters to check the data's Internet Protocol (IP) address, domain name, and protocols such as Hyper Text Transfer Protocol (HTTP), World Wide Web (WWW), or File Transfer Protocol (FTP). Firewalls can also be used to filter certain protocols like Transmission Control Protocol Internet Protocol (TCP/IP), Internet Control Message Protocol, User Datagram Protocol, Simple Mail Transport Protocol, and Telnet.
A firewall works by creating inclusive and exclusive rules. An inclusive firewall only allows traffic that matches the rules and blocks all the other websites. An exclusive firewall is the opposite and permits entry of all websites except those that match the rules.
Companies/Brands
SonicWALL, CISCO, ZoneAlarm, and NetGear provide firewalls.
Resources
