How are intrusions done ? How does my firewall protects me ?[Bearbeiten]
- A computer, when looking at the net part of the beast, is looking like a giant telephonic standard. What could be considered as the main phoneline's number is your IP address. Each desk is is called a "port".
So if you want to get a web page from a server (eg. the google start page), you will call google's IP address and ask for port 80 (that's the default port for web pages). A connexion shall be established, and your browser will ask for the wome page, which the server will return.
The problem is that the standardists aren't allways that trustable : some might have bugs, and when called in a specific way, or when told a specific string of uncommon characters, a bug shall occur. The attackant, which had feeded the faulty data, can take advantage of that bug to take control of the computer.
A firewall protects you from such attacks by blocking all ports exept those that are really needed. This way, your programs can't listen on those ports, and can't be affected by these attacks.