Almost everyone who deals with the computer, and it was only by surfing the Internet or playing with friends has ever heard of a firewall. But what is really behind it and how does a firewall your computer safe? To address this question, one must for most people once PRESS, how to connect to other computers, for example via the Internet, work at all. This is not just a line that is sometimes open when it is needed and otherwise does nothing. Quite the contrary! On a network connection, there is almost always a lot of traffic with the exchange of data. The computer such as regularly ask whether everything is still there or whether it has changed something in his environment.
Just as he responds to requests from elsewhere. And these questions are the problem. Maybe one or the other ever heard of the term Port. A network connection has many different access points. This only logical points called ports.
They are numbered and each port is designed for data transmission. Sun requests when browsing the Internet on port 80 are provided as an example. There are at any operating system port to which the computer responds and thus is susceptible. If you want to turn those questions would need to either reprogram the operating system (possible in very rare cases) or just switch to another system in between. Just such a system is a firewall. It blocks including inquiries on the ports that are considered unsafe. Testing can be the safety of their own PC’s with a firewall test that examines the various ports are open and whether they pose a danger.