What is a Firewall?
By infohub — Dec 10th, 2017
A firewall could be a hardware piece or software which helps screen out viruses, worms, and hackers attempting to enter your computer system via the Internet. In other words, it’s a device developed for network security and monitors all outgoing and incoming traffic while deciding if specific traffic should be blocked or allowed basis certain security rules.
History of firewall
For more than 25 years, firewalls have served as the main tool for network security all over the world. Developers and users trust firewall because it creates a wall between controlled and trusted internal networks and uncontrolled external networks like the Internet.
The word ‘firewall’ was borrowed by the computer security industry from fire prevention and firefighting- firewalls are barriers developed for preventing the spreading of fire.
As organizations started to shift from dumb clients and mainframe computer systems to client-server models, it became crucial to monitor server access. Firewalls came up in the later part of the 1980s. Prior to that, the only way to ensure network security over the Internet was through ACLs or ‘access control lists’. ACLs helped in deciding if an IP address should be given or denied network access.
Types of firewalls
Some of the most commonly used firewalls include the following:
- Circuit-style gateway implementation
The process is used for applying security techniques in case of the establishment of a UDP or TCP connection. After the connection is made, packets are allowed to flow between hosts without any additional checking.
- Packet filtering
In this system, each packet that leaves or enters the network is assessed and is accepted or rejected basis user-defined rules. This type of firewall is quite efficient and transparent, yet hard to configure. A packet-filter firewall will operate primarily on the OSI model’s first 3 layers (network, data-linked, and physical). However, the destination and source port numbers are obtained by the model’s transport layer.
- Proxy firewall
Proxy firewall is one of the original firewall devices and works as a gateway between networks for a particular application. These servers have the ability to offer additional functionality like content security and caching since they prevent direct connectivity with external networks. But, this could have an impact on the throughput applications and capabilities supported by them.
- UTM (Unified Threat Management) firewall
This type of firewall generally combines the functions performed by an antivirus and intrusion prevention with that of an inspection firewall. It might also incorporate extra services, including cloud management. UTMs are known for focusing on user-friendliness and simplicity.
- Application-layer firewalls
With the increasing attacks on web servers, there has been a redevelopment of firewalls so that they can fiercely protect servers as well as their applications, and not just the network resources running them. It was in 1999 that application-layer firewall was first introduced. It allowed firewalls to assess and accept/reject packets on all OSI layers.
The main advantage of this type of firewall is that it is effective in blocking specific content, like certain websites or identified malware. It can also inspect whether there is any misuse of certain protocols and applications like DNS, FTP, and HTTP.
In practice, most firewalls will utilize a combination of the above techniques to offer protection from cyber attacks. In Mac OS X and Windows, the operating systems will have internally built firewalls.
You can also get third-party protection packages such as Norton Personal Firewall, Black Ice Protection, Zone Alarm, McAfee Personal Firewall and others. Most of them provide free trials or versions (commercial versions).