A firewall is a type of security mechanism used for preventing security threat in both incoming and outgoing computer traffic. It protects your computer system and/or the private network from intrusions.
It acts as a barrier, which checks all the incoming and outgoing information to and from your computer or a network based on the firewall configuration settings. Firewalls can be customized according to the level of security required. It filters the messages based on some conditions, such as the IP address, ports, protocols, domain names etc.
These can be implemented in the hardware, software or sometimes both and scan the entire messages passing through it and verify whether each block or packet of the message meets the specified security criteria.
Some operating systems like Microsoft Windows offers built-in firewalls, which are by default turned on to block incoming threats from the Internet. You can also look for any third-party software or hardware firewall to replace the default Windows firewall.
Types of firewall
There are various types of firewalls like:
1. Packet filtering firewall
2. Application-level gateways
3. Circuit-level gateways
4. Hybrid firewall
The role of packet filtering firewall is to examine the information available in the header of the message packets. The Application-level gateway firewall works on the application layer of the protocol stack. It works in a more intelligent way as compared to the packet filtering firewall.
Mentioned below are some of the conditions, which help in adding or removing the filters from the firewall:
1. IP address: Every machine connected to Internet has a unique IP address. You can customize the firewall to block any IP address, if it seems to show an uneven or unauthorized attempt or nature.
2. Protocols: You can decide which protocols to be included in your firewall’s filters. Some of the commonly used protocols, which can be included in the firewall, are: IP, HTTP, TCP, FTP, SMTP etc.
3. Ports: You can configure the firewall to allow or block any port number.
Similarly, there are various other conditions which can be used to configure the firewall.