Before we talk about the weaknesses of firewalls it is crucial to know and see to understand how a firewall is setup and how it actually works.
Simply put, a firewall is either a software or a hardware based security system for networks, that is tasked with regulating the flow of incoming and outgoing network traffic.
In order to decide which data packets should be allowed through and which should be prevented, the firewall carries out a proper analysis that is based upon an applied set of rules.
Basically, the definition of a firewall can be stated in a variety of different terms, depending primarily upon your level of understanding of computer networks.
Primarily however, a firewall creates a sort of a barrier between a network of computers that can be trusted, as well as an external network, such as the internet, which cannot be trusted.
In case somebody tries to send in data packets that are infected with viruses, the firewall will automatically detect them and prevent them from entering the secure network.
Primarily, most individual computers come with a firewall based security system that can be turned on or off at your behest. Hardware such as routers are also installed with firewalls to prevent access.
As mentioned above, a firewall is created to protect a system from any harmful threats from another network.
It acts as a sort of barrier.
However, it can't fend off attacks that are launched from within the system that it is supposed to protect.
This is quite a common issue.
Imagine if someone gains unauthorized access from within the network or no authorized use of the network, the firewall is deemed useless in such cases.
A firewall is no stronger than the correct configuration being setup.
If the user do not have a full understanding about how to setup the firewall configuration and set correct port permissions.
If leaving too many ports open for remote access services or SQL database it can lead to full system compromise.
A firewall is no stronger than the configuration it has setup.
The user might be thinking the firewall is correct setup but it is required to do a full scan of the firewall afterwards.
Only by doing a full scan from a remote site it is possible to verify if the firewall configuration is setup correctly.