A firewall is a security system that protects computers and networks from unauthorized access. It does this by monitoring the data traffic between the local computer and external networks such as the internet. Its main task is to defend against malicious software like viruses or spyware, as these could attempt to steal sensitive data or disrupt computer systems.
How a Firewall Works
The firewall serves as a control instance: It checks the access rights for programs and external computers. It decides which data packets are allowed to pass and which are blocked. The configuration determines whether programs are allowed to access the internet. The firewall also regulates communication between computers in the network.
Firewalls do not initially distinguish whether access is harmful, but act based on established rules. These rules relate to:
- Access rights: By default, firewalls block foreign IP addresses that request access. Users can manually add exceptions.
- Installation queries: Programs that access the internet require confirmation. This ensures that no malware is installed.
- Network visibility: In public networks, it can reduce the visibility of the computer to make attacks more difficult.
- Blocking active content: Technologies such as ActiveX or Flash can be blocked to prevent the execution of potentially harmful content.
Ports
Firewalls regulate data traffic through ports. Each program uses specific ports that can be opened or closed as needed. This prevents unwanted data traffic, but can also lead to program errors if required ports are not opened.
Types of Firewalls
There are two main types of firewalls:
The Personal Firewall is installed on the computer, monitors data traffic, and prevents unauthorized access. It is often part of the operating system. External Firewalls, on the other hand, are positioned between the home network and the internet: They analyze incoming data traffic and stop threats before they reach the network. Typically, these firewalls are integrated into a router.
Limitations
While firewalls provide basic protection, it is advisable to combine them with antivirus programs. These detect and block malware based on current virus definitions, providing more comprehensive protection.
