The effectiveness of your firewall thus depends on how you configure it. The following are some of the many different options available:
- Access rights for remote IP addresses: Any access attempts by other computers in the network are identified by an IP address and are initially blocked by default. If the data transfer is desired, you can manually authorize it or add the IP address as an exception so that access will be permitted the next time without being prompted.
- Access requests from online programs: You should have manual confirmation set for installing programs found online. This way you can be sure that you are installing the file you want, and you can immediately detect when an untrusted website is trying to infect your computer with malware.
- Network visibility: You can set the visibility of your computer on networks. We recommend hiding your computer in public networks (e.g. WLAN hotspots in airports or cafés) to provide additional protection from access attempts. While visibility is not the same as having access permissions, it does mean that it is easier for attackers to target your data.
- Blocking active website content: Some technologies (e.g. Microsoft ActiveX and Adobe Flash) used for displaying dynamic website content, such as videos and graphic animations, are frequently exploited to spread malware because the content runs locally on the user’s computer. You can block the execution of this content in advance.
Those are just some of the settings you can define in your firewall’s software configuration. Naturally, in addition to blocking websites, services and IP addresses, you can also define them as trustworthy and thus allow automatic access. This illustrates the limitations of a firewall – to reliably block malware, you need to correctly assess other programs and computers accessing your computer.
For this reason, you should not depend exclusively on a firewall. You should also use a reliable antivirus program that compares both installed programs and dynamic website content with current virus definitions and blocks them or warns you before executing them when necessary.
Many firewalls also work with ports. In order for a data packet from the internet to reach your computer, it must pass through one of these entrances. Each application uses a specific port. A firewall can be configured to ensure that only the required ports can be opened. The firewall will block all other entrances and prevent applications from accepting undesired or unplanned data packets. This regularly results in programs not working due to the firewall. However, if this occurs, you should not disable the firewall. Instead, just open the required port.