Firewall

A firewall is a piece of computer software or hardware that is designed to monitor connections between computer networks to provide protection from malicious software or attacks from hackers. Essentially, a firewall is a sort of security gateway through which data must pass in order to enter a private network. A firewall examines all incoming data, determines if any of this data presents a potential threat to the network, and filters out anything it deems to be dangerous. Firewalls were first developed in the 1980s as the number of potential external threats began to grow at a staggering rate. Since that time, firewalls have become a standard part of the broader network security systems that commercial and individual computer users depend on to protect their data from external dangers.

How a Firewall Works

At the most basic level, a firewall is a relatively simple mechanism that works as a filtering device. When a network is connected to the Internet or another network, it regularly receives data packets, which are small units of information that travel along a given network path. In addition to its main data, which is referred to as the packet payload, each data packet contains a packet header that provides key information about its type, size, source, and destination. In practice, the firewall examines each data packet that attempts to enter a network and determines whether or not it complies with a set of rules defined by the firewall administrator. If a given data packet satisfies the rules in question, it is allowed to pass into the network. Otherwise, it is denied entry and discarded. This process is called packet filtering.

Typically, firewalls carry out the packet filtering process according to a deny-by-default/allow-by-exception security philosophy that revolves around a series of carefully designed rules. While many of these rules define what the administrator wants to allow, others define what is to be specifically denied. In short, if a data packet matches an allow rule, it is allowed to pass through into the network. If a data packet matches a deny rule, on the other hand, it is blocked from entering the network and discarded. Furthermore, a data packet can also be dropped if it does not match any rules at all. This rule, often known as the final rule or the deny-all rule, is the main guiding principle by which a firewall operates.

In addition to preventing potential threats from getting into a network, a firewall also monitors outgoing connections to ensure that a threat that is already inside a network cannot do further damage. Certain types of malicious software send out a signal when they become implanted in a network. This signal can allow the software's author to trigger damaging actions or even completely control a computer from a remote location. If it is properly set up to do so, a firewall can detect such a signal so that the malicious software can be shut down before it causes serious, potentially irreversible damage.

Finally, a firewall can also log the traffic that passes through it. As data packets pass through or are discarded by a firewall, it logs each one to create a clear picture of the traffic a network experiences. This information can be useful in a number of ways. It might, for example, be used to track the source of an external attack. In a commercial setting, an administrator might also use a firewall log to monitor employees' online habits as a way of minimizing lost productivity.

Development

Firewall technology was first developed in the 1980s in response to the growing number of external threats faced by computer networks at the time. Realizing that the rapid proliferation of these threats presented a major problem for computer users, tech companies like Cisco Systems and Digital Equipment Corporation set out to devise a way to minimize the threat of viruses and hacker attacks. Their solution was the so-called network layer firewall, which reviewed and sorted data packets using basic details such as their source and connection type. Although this approach initially proved successful, it quickly became apparent that network layer firewalls could be circumvented easily. This eventually led to the development of application layer firewalls in the 1990s. Although they followed the same basic premise as their predecessors, these firewalls were designed to provide a more exhaustive assessment of incoming data packets. Many later firewalls combined elements of the network layer firewall and the application layer firewall to form a more efficient and effective hybrid product.

Limitations

Although firewalls can be an important tool for network security, there are some common misconceptions about what they do and how much protection they actually provide. Many computer users mistakenly believe that firewalls can weed out all external threats and completely secure the networks on which they are installed. In reality, however, a firewall simply functions as a basic gatekeeper that is designed to keep out any data packets deemed to be a potential threat based on a specific set of exceptions. A firewall is not an antivirus program or some other type of program that is equipped to scan all incoming information for potential threats. As such, firewalls cannot offer guaranteed protection. Even data packets that a firewall might normally identify as a threat can be disguised, enabling them to gain entry into a network. This all means that a firewall should be seen as only one part of a broader network security scheme that should also include antivirus protection and other threat detection utilities. In short, a firewall's effectiveness is dependent upon its use with other methods of network security.

Bibliography

"Firewall." Britannica, 9 Jan. 2025, www.britannica.com/technology/firewall. Accessed 24 Jan. 2025.

Kazmeyer, Milton. "What Is the Purpose of a Firewall?" Houston Chronicle. Hearst Newspapers, LLC. Web. 29 Feb. 2016. http://smallbusiness.chron.com/purpose-firewall-53858.html

Munson, Lee. "What Is a Firewall and Why Do You Need One on Your Home Network?" Comparitech. Comparitech. 17 Sept. 2015. Web. 29 Feb. 2016. https://www.comparitech.com/antivirus/guides/what-is-a-firewall-and-why-do-you-need-one-on-your-home-network/

Stewart, J. Michael. Network Security, Firewalls, and VPNs. 2nd ed. Burlington: Jones & Bartlett Learning, 2014. Print.

Whitman, Michael E., Herbert J. Mattord, and Andrew Green. Guide to Firewalls and VPNs. 3rd ed. Boston: Course Technology, 2012. Print.