In reality, a firewall is supposed to protect against IT attacks, but often the exact opposite happens and the firewall becomes a gateway. Like almost every system, a firewall also has loopholes that attackers can exploit for their own purposes.

What should companies pay special attention to? And how should they best organize their firewalls?

This article provides an overview of the three most common firewall vulnerabilities and how companies can protect themselves.

To recognize common weaknesses, you need to consider what the actual purpose of a firewall is: A firewall is a security system that protects networks primarily from the outer perimeter, which is the interfaces with external networks, usually the Internet.

A firewall defines the rules for transferring data between systems and prevents unwanted access. These rules primarily concern source and destination IP addresses, as well as IP port numbers. Firewalls are elementary components of IT security concepts.

Often the problem is not the technology itself. Vulnerabilities occur in many companies, especially in firewall management. One of the most common weaknesses can be found in the basics: choosing firewall rules. And the wrong choice. If potentially dangerous sender IP addresses are not identified as such and can easily send data packets across a company's network, even the best firewall will not help.

The following applies here: it is better to have too many prohibitions than one dubious permission. The rules apply in a certain order. In most cases from top to bottom. This is critical to ensuring the security of systems. For example, if a connection is allowed in a top-level rule, it can no longer be denied below.

Some rules are correct and important, but initially they are independent. Since they allow for communicative relationships, the context of the rules must also be taken into account.

The question arises: what is the purpose of the rule and why is it applied at this particular point in the sequence? And this is where the second common weakness lies: without clear documentation, employees often can no longer understand why a rule exists. If firewalls or systems change, the rules are no longer questioned and are simply accepted.

In addition to documentation, you should regularly review your firewall rules. Because this is where vulnerability number three lies: systems, such as web portals, change from time to time. Even without notifying or informing administrators.

A regular process that checks at least once a year to see which firewall rules are still needed is critical. Otherwise, holes may appear in the firewall affecting the security of the systems.

The good news is that all of these vulnerabilities can be avoided. For example, through the four eyes principle when creating firewall rules. To ensure that knowledge does not belong to just one or two people, all rule information must be documented in a way that can be understood by a third party expert.

An internal audit is also recommended, which is carried out not by the employees themselves, but by fellow specialists. This also allows you to directly check whether the documentation is understandable to a third party and therefore sufficient.

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