What Is a Firewall?
A firewall is a computer security system that monitors incoming and outgoing network traffic based on predetermined rules. A firewall can be hardware or software based and acts as a barrier between your trusted internal networks and untrusted external networks such as the internet. Firewalls can block unauthorized connections to a computer or network and allow legitimate ones. They can also be configured to send a warning to users who attempt to connect to dangerous sites or programs.
The most basic firewalls are packet-filtering systems that analyze the contents of data packages sent over the internet to ensure they are safe and that a network is protected from various types of malware. More advanced firewalls, such as stateful inspection, create a table of what has been seen and learned, meaning they can make more in-depth decisions about the safety of packets and other forms of data. These more robust systems can even be used to neutralize specific types of malware.
Proxy firewalls, on the other hand, are unique in that they read and filter application-level data (layer 7). These devices can identify a host’s identity, examine file sizes, and even run a small piece of code inside a closed-off environment to ensure it is not malicious.
The most common firewall type is one that runs on the host computer itself and can be found in various software vendors’ offerings. Often, these are bundled with other cybersecurity features like antivirus protection and antimalware. The firewalls found in these products are typically easy to install, but they are limited in their ability to protect against malware. This is why a multi-layered approach to cybersecurity is often recommended and encouraged.