Firewall and its type

What is a Firewall? Explain Hardware and Software Firewall

Firewall

Firewall is a software or hardware or combination of both hardware and software. A private network (LAN) connected to the internet is in high risk to intrusion by unauthorized users on the internet. To protect the information from being leaked, all the messages or communication entering or leaving the private network must pass through a firewall which authenticates the traffic based on set policies or security criteria. Firewall is system that protects a private network from internet by filtering the incoming and outgoing messages based on security mechanism as set by administrator. The firewall can be a software application or it can be in the form of a hardware device.

Hardware Firewall

It is a hardware device that is placed between internet and intranet (LAN). It is a standalone device that is configured to protect multiple systems in an organization. An example of a simple hardware firewall is a broadband router and there are professional high-cost hardware firewalls also called UTM (unified threat management) that provides a single management console to monitor various security related applications. UTM firewall provides intrusion protection, anti-virus, anti-malware, spam, VPN and content filtering in a single console. Only IT professionals can configure and manage these UTM firewalls

Software Firewall

For a home or small networks, you can use software firewalls which can be installed on individual systems or a server. Software firewalls are easy to install and update as compared to their hardware counterparts. Even if there is a hardware firewall installed in your office, you must install a software firewall since a hardware firewall works only in your office (LAN) and if you are traveling or working outside your office, it is the software firewall that will provide protection to your system from external threats.

A basic software firewall is available free with windows operating system but you can also buy advanced software firewalls like McAfee, Norton Internet security, Bitdefender internet security or Kaspersky internet security.

Types of Firewall

Packet filtering firewalls 

This firewall doesn't route packets, but instead compares each packet received to a set of established criteria -- such as the allowed IP addresses, packet type, port number, etc. Packets that are flagged as troublesome are, generally speaking, unceremoniously dropped -- that is, they are not forwarded and, thus, cease to exist. This, the original type of firewall, operates inline at junction points where devices such as routers and switches do their work.

 Circuit-level gateways 

Using another relatively quick way to identify malicious content, these devices monitor the TCP handshakes across the network as they are established between the local and remote hosts to determine whether the session being initiated is legitimate -- whether the remote system is considered trusted. They don't inspect the packets themselves, however.

Stateful inspection firewalls

State-aware devices, on the other hand, not only examine each packet, but also keep track of whether or not that packet is part of an established TCP session. This offers more security than either packet filtering or circuit monitoring alone, but exacts a greater toll on network performance.

A further variant of stateful inspection is the multilayer inspection firewall, which considers the flow of transactions in process across multiple layers of the ISO Open Systems Interconnection seven-layer model.

Application-level gateways 

This kind of device, technically a proxy, and sometimes referred to as a proxy firewall, combines some of the attributes of packet filtering firewalls with those of circuit-level gateways. They filter packets not only according to the service for which they are intended -- as specified by the destination port -- but also by certain other characteristics, such as the HTTP request string.

While gateways that filter at the application layer provide considerable data security, they can dramatically affect network performance.