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Firewalls are software or hardware that works as a screening system for the data attempting to enter a computer or network from the external world. Firewalls are based on predefined security policies and cannot move on its own accord. Instead, it follows programmed rules created by humans that are modified systematically to become feasible to prevent malicious damage to a computer or network. When any network traffic is suspected as a potential security threat, the firewall prevents it from entering the network or reaching the computer.Firewalls date way back to the early days of the internet, when the World Wide Web was known as the Advanced Research Projects Agency Network (ARPANET). The first generation of firewalls was used in the early 1990s which used to work on a set of simple predefined rules that controlled outside access to internal company resources.

It was defined as a packet-filtering system and designed by the engineers from Digital Equipment Corporation and the filtering was done by looking at the destination address, its protocol and the port number used.But these were susceptible to IP spoofing, where an intruder tries to gain unauthorized access to computers by sending messages to a computer with an IP address indicating that the message is coming from a trusted host.

This left the potential for a vulnerability to be exploited. Technology advances with the passage of time creating new demands and overcoming limitations. Through continuous evaluation and research, rectifications and updates were initiated to the principle of firewalls to meet the need of its users.Today, what we call next-generation firewalls focus on deep packet introspection. Features such as intrusion detection and prevention, user identity integration and enhanced virus protection forms part of this. The addition of Virtual Private Network in firewalls became a widespread practice by companies since this allows off-site employees to access company resources when communicating over insecure network connections such as public Wi-Fi. This combination of intrusion detection, antivirus, email filtering and other functions into a firewall formed the unified threat management (UTM) theory introduced in 2004.

The most recent category of firewalls has been termed as stateful multilevel inspection, or SMLI. SMLI’s unique approach screens the entire packet and rapidly compares each packet to known bit patterns of friendly packets before deciding whether to pass the traffic.Firewalls have evolved from mere packet-filtering mechanisms to the modern day end-point security solutions and formed an inevitable part of present day cyber security. Whatever generation of firewall do we use currently or consider, the most important thing is to match the product with the specific security requirements of the organization.

It is not advisable to pay for more than what is needed or end up with less protection than the organization demands.The overwhelming response of the internet has seen a new dawn into the digital world but we need to be careful of computer hacking that might result in the loss of personal or business records or unauthorized access of our valuable data and information. However, the borderlines of modern networks are spreading outside the firewall perimeter. Most networks today possess a well defined structure consisting of the inside or trusted zone, the outside or untrusted zone and other optional intermediate security zones. This topic shall be taken up later.