What is a firewall? Understanding the security measure that protects against cyber threats

What is a firewall? Understanding the security measure that protects against cyber threats
A firewall is an important security feature for protecting your devices against cyberattacks.Maskot/Getty Images
  • A firewall is a key cybersecurity feature for protecting a home or office network from malware and other online threats.
  • There are distinct forms and types of firewalls, and some are considered more secure than others.

Many of us live with the fear of a cyberattack disrupting our computer-dependent lives - not to mention their potential to wreak havoc on an entire country.

Fortunately, we have security measures like firewalls, which prevent bad actors from gaining unwanted access to networks.

Preventing your internet from crashing isn't the only positive you can gain from a network firewall. There are also customizable uses for firewalls, like blocking inappropriate online content from your children.
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Here's what you need to know about firewalls, including how they work and why they're important.

Firewalls, explained

A firewall is like a bouncer for your internet activity, creating a security barrier between your home network and unwanted intrusion from the internet at large.

Firewalls can be cloud-based, or they can be a physical piece of hardware that you buy and connect to your modem and router. (For the most part though, modems and routers will come with pre-implemented firewall technology.)
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If you've ever tried to set up your own server with port forwarding, for instance, you may have been foiled by your router's firewall.

What is a firewall? Understanding the security measure that protects against cyber threats
A firewall can protect all your family's devices.Stephen Swintek/Getty Images
Your computer will also in all likelihood come with its own proprietary firewall, like the Windows Defender Firewall that comes installed on Windows PCs. There are many types of firewalls, but the gist of how they work is similar: a firewall works by closing your network off by default to most internet traffic, or at the very least, requesting your permission before allowing the traffic in.
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Different types of firewalls

Among the distinct forms and types of firewalls in use today, the following are some of the most common.

  • Packet-filtering firewall: This is the most ubiquitous type. This firewall inspects packets, or bundles of data, and either denies or allows their passage through to the network depending if the packet abides by the firewall's pre-determined security parameters. The firewall is able to make determinations by examining the packet's origin and destination IP addresses.
  • Stateful and stateless firewalls: Within the packet-filtering firewall are two subtypes: stateful and stateless. Because stateless firewalls see packets on a case-by-case basis, never retaining their information once inspected, they're considered an easier target for hackers. That's unlike stateful firewalls, which maintain information about packets they've inspected previously.
  • Next-generation firewall: The evolution of firewalls is the NGFW, short for next-generation firewall. These firewalls are mostly associated with the corporate world; however, open-source NGFWs are making them accessible elsewhere. The NGFW features advanced tech; for instance, it offers surface-level and deep-packet inspection, where the actual content of the data packet is examined, or an automated intrusion prevention system that can halt a network attack.
  • Proxy firewalls: These act as a middleman between your computer and the internet. The proxy firewall essentially masks your identity by acting as your proxy, concealing your location and IP address whenever you visit a website or application. A proxy firewall is useful for online personalities, for instance, like Twitch streamers not wanting to get doxxed.

Why firewalls are increasingly important

Having some kind of firewall as a line of defense for your home network has become increasingly important as more devices are internet-enabled. After all, you don't want to worry that your porch's smart light bulb - which you installed as a means to dissuade burglars - is creating a cybersecurity loophole in your network.

What is a firewall? Understanding the security measure that protects against cyber threats
A firewall acts like a shield for your internet network and devices.sarayut Thaneerat/Getty Images
There are benefits beyond security as well: A properly configured firewall can keep your internet running more quickly by routing traffic more efficiently.
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Finally, a firewall can also be programmed to act as a content moderator for kids by restricting their access to certain websites. Those sorts of settings won't be standard for a firewall, but can be configured with most of them.

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