What is a firewall?

A firewall is a program or hardware device that protects a computer system by managing network traffic based on predefined rules and blocking suspicious activity. Essentially it works as a filter or a protective layer between a trusted network (home or work) and untrusted network (eg Internet). The firewall prevents unauthorized access to the system.

Types of firewalls

  • hardware firewalls
    Usually it is a separate device, although more often can be found on majority of modern routers and it is an important part of network security.
  • software firewalls
    On contrary it’s a software program sometimes also a part of operating system. The example of software firewall is Windows Defender.

Firewalls functions

package filters

The package filters belong to first generation of firewalls and manage traffic according to the rules defined in firewall’s settings. Suspicious packages are rejected (with or without notification to the sender). The traffic can also be filtered by the source address (IP and port), destination address (IP and port) or protocol. From a practical point of view, they pay off on a small scale, but management can become messy and complicated to large.

stateful filters

Stateful filters are the next (second) generation of firewalls. They operate at a higher level than packet filters. They analyze traffic in more detail. Stateful filters ensure that packets are sent in the correct order. In addition, they keep track of sessions and reject traffic from an unauthorized source.

DDoS attacks is one type of the attack that this type of firewall has to deal with.

application level firewalls

Application level firewalls are the most advanced third generation firewalls. The main advantage of this type of firewall is the understanding of the application. They can detect suspicious activities, such as incorrectly used ports or inappropriate protocols.

Windows Defender tips:

How to switch off/on Windows Defender firewall?
  1. Open Windows (Defender) Firewall.  [Windows 10 shortcut: click Start, type “firewall” and choose it from list].
    • Go to Control Panel.
    • Next click System and security.
    • Choose Windows (Defender) Firewall.
  2. Choose “Turn Windows Defender Firewall on or off”.
  3. Select “Turn on Windows Defender Firewall” or “Turn Off Windows Defender Firewall” in both private and public network settings depending on your preference.
How to allow website through a Windows Defender?

Windows Defender firewall allows you to manage applications and programs, as well as to create rules that can block selected IP addresses. However, you should keep in mind that almost every anti-virus program (and not a firewall) allows this type of activity (blocking the site, which can be potentially dangerous). So that’s why it’s very important to check the settings of the installed antivirus program.


Network security is a very important part of any computer system. The firewall plays a key role in this, acting as the first level of protection. It filters unwanted and untrusted traffic while protecting computer system.



Pablo Web
I am a software engineer in Warsaw. I'm passionate about Informatics. I like taking photos, making videos and cooking.

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