This graduation thesis is about the firewall which acts like a barrier between the user and network traffic. The thesis is written starting from the basic terms all to the more detailed terms like: what is a firewall, what is it for, types of firewalls, specifications, handling firewalls, firewall protection, functions, connecting scheme, future of firewalls and other. After finishing the thesis one can easily get to the conclusion how firewalls are an inevitable part of the network security without making any difference who the end user is (just one or maybe an whole organization). The conclusion is how the network threats have rapidly evolved and how the’re causing massive business losses and how firewall are keeping up with the threat for providing a quality protection and better tomorrow.