A firewall is a security system that protects computers and networks from unauthorized access. This is done by monitoring data traffic between the local computer and external networks such as the internet. Its primary task is to defend against malicious software such as viruses or spyware, as these could attempt to steal sensitive data or disrupt computer systems.
The firewall acts as a control instance: it checks access permissions for programs and external computers. It decides which data packets are allowed through and which are blocked. The configuration determines whether programs are allowed to access the internet. The firewall also regulates communication between computers on the network.
Firewalls do not initially distinguish whether access is malicious; instead, they act based on predefined rules. These relate to:
Firewalls regulate data traffic via ports. Each program uses specific ports, which can be opened or closed as needed. This prevents unwanted data traffic, but it can also lead to program errors if required ports are not enabled.
There are two main types:
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 traffic and stop threats before they reach the network. Typically, these firewalls are integrated into a router.
Although firewalls provide basic protection, it is advisable to combine them with antivirus software. This detects and blocks malware based on up-to-date virus definitions, providing more comprehensive protection.
