What is a firewall?

A firewall is the digital bouncer between your device or home network and the internet. It monitors all data traffic and decides, based on predefined rules, which connections are allowed, and which are blocked. In this way, unwanted access, insecure services and attacks can be effectively contained, without you having to give up everyday convenience.

23.10.2025 | Reading time: 5 minutes

How does a firewall work?

To turn a rigid barrier into intelligent protection, a firewall inspects data traffic on several levels. First, sender, recipient, protocol and port are checked. It then keeps track of ongoing sessions and recognises whether a packet belongs to a legitimate connection that you initiated. Modern systems go even further: they also analyse the application layer, detect patterns of certain apps and block risky content or suspicious activities.

This creates a context-aware filter that enables everyday use but reliably stops attacks. In corporate environments, firewalls are often additionally combined with Intrusion Detection Systems (IDS) or Intrusion Prevention Systems (IPS) to achieve an even higher level of security.

What types of firewalls are there?

Firewalls differ in their structure and area of use.

Software firewalls run directly on the end device and offer fine control per application. They are particularly suitable if you want to specifically secure individual computers or laptops.
Router firewalls are integrated into the internet router and form the first layer of protection for your entire home network. They usually work unobtrusively in the background and are therefore the foundation for every household.
Hardware firewalls are standalone devices that protect the home or company network at the boundary to the internet. They allow segmentation, meaning the separation of smart home devices, work environment and guests.
Web application firewalls (WAFs) are aimed at operators of websites and online shops. They detect typical attacks such as SQL injections or cross-site scripting, but they do not replace secure coding.

Many modern solutions combine the functions of classical systems in so-called Next Generation Firewalls (NGFWs), which also offer advanced attack detection and centralised management.

Do you even need a firewall at home?

Yes, a firewall is now considered a basic measure of IT security. Your operating system already comes with a software firewall, and home routers usually block incoming connections automatically.

With a strongly secured Wi-Fi, regular updates and an activated router firewall, you achieve a solid level of security. However, if you need more control, insight into data traffic or the separation of different networks, a hardware firewall can be useful.

Differences between software, router and hardware firewalls

A software firewall protects a single device very precisely. It allows you to define app-specific rules and respond immediately if something suspicious happens.
The router firewall sits at the transition between the home network and the internet. It automatically protects all devices, combined with NAT, which makes internal IP addresses invisible to the outside.

A hardware firewall goes further: it offers more performance and allows the home network to be divided into different segments, for example, for smart home, work devices or guests. The combination of all three variants provides the best protection.

Using the firewall effectively in everyday life

Effective use does not require complicated technology, but clear principles:
keep the router firewall active, leave the software firewalls enabled on all devices and schedule regular updates for operating system, apps and router firmware.

Secure your Wi-Fi with a current standard such as WPA3 or at least WPA2 AES and a long, randomly generated password. Set up a separate network for guests and smart home devices to isolate risks. If you work in a home office or want extended logging, a hardware firewall provides additional visibility and control.

Best practices for firewall rules

A firewall is only as strong as its configuration. Therefore, allow only the connections that are truly necessary, and keep exceptions limited and transparent. Logs help you identify recurring anomalies and take targeted countermeasures. For remote access, a VPN is indispensable.

It is also advisable to think in terms of security zones: unknown or insecure devices should be treated as if they were directly connected to the internet.

Limitations of the firewall

A firewall is a central component, but not a cure-all. It does not replace regular updates, strong passwords or cautious behaviour. Attacks via phishing emails, manipulated attachments or carelessly shared cloud folders can still occur despite a firewall, if the user actively allows them.
A web application firewall also protects against typical attacks but cannot compensate for programming errors. Only a multi-layered approach with patches, password manager, multi-factor authentication, antivirus and firewall ensures comprehensive protection.

Quick security check for your home

A brief overview to secure your home network in just a few minutes:

Make sure the router firewall is active and no unnecessary ports are open.
Protect your Wi-Fi with WPA3 or WPA2 AES and a long password, and disable WPS.
Enable a separate guest network for visitors and smart devices.
Keep all systems – from the router to the smartphone – regularly updated.
Check the firewall logs from time to time to detect unusual activities.

Firewall as the cornerstone of your digital security

The firewall forms the first line of defence for your home network. It separates safe from risky connections, makes data traffic transparent and significantly reduces the attack surface.
With an active router firewall, operating system firewalls enabled, a secure Wi-Fi and regular updates, you already achieve a solid level of security.

Those who also value transparency, segmentation and centralised control can complement their setup with a hardware firewall. Combined with additional protective measures such as multi-factor authentication and antivirus, your digital home remains stable even when the internet gets stormy.

FAQ about the firewall