Understanding the Firewall: Your First Line of Defense

Computers communicate with each other to send and receive information — without this communication, you wouldn’t be able to do the things you want to do on the web: login to a website, perform transactions, transfer files, receive email, open files, etc. Making this all happen requires that computers send and receive data “packets” from one another — but how do you make sure the information being sent or received is safe? One answer is the firewall.  

What Is a Firewall?

A firewall is hardware or software (or both) security system that acts as your computer’s or your application’s first line of defense by screening out hackers, viruses, worms, and malware that try to reach your computer through network traffic — or over the Internet. What does or does not pass through is based on a defined set of security rules.  

The easiest way to think of a computer firewall is to compare it to its firefighting origins: in firefighting, a firewall barrier is created to prevent the spread of fire. With computers, a firewall does the same thing — it creates a barrier between your computer and everything it communicates with: secured and controlled networks, trusted and untrusted external networks, the Internet, etc. Only traffic that’s defined in the firewall policy is allowed — everything else is denied access to your machine.

Thanks to the growth of the Internet — and ever-changing sophistication of cyberattacks — firewalls have had to evolve quite a bit since their emergence in the late 1980s. Just take a look at the categories and types of firewalls in existence:

Categories of Firewalls

  1. Network Firewalls

These filter traffic between two or more networks, and are positioned on the gateway computers of LANS, WANs and intranets. They made be software or hardware-based.

  1. Host-Based Firewalls

This type of firewall runs on host computers and controls network traffic in and out of those machines. They are positioned on the network node.

Types of Firewalls

  • Packet Firewall (1st Gen: 1988)
  • Stateful Inspection Firewall (2nd Gen: 1980-1990)
  • Application-Layer Firewall (3rd Gen: 1994)
  • Proxy Firewall
  • Unified Threat Management (UTM) Firewall
  • Next Generation Firewall (NGFW)
  • Threat-Focused Next Generation Firewall

Firewall Protection

Firewalls are intended to prevent malicious traffic — like malware — from reaching your computer and its valuable resources. Some only offer inbound protection, while others offer both inbound and outbound protection. With that in mind, it’s always important to not only make sure your firewall is active (especially on public WiFi), but to see how you’re protected (inbound versus outbound). Stay tuned for more on firewalls, including the role they may play in the future of network security.