The Wall of Fire

Each and every, recent, computer has a firewall installed lately. Windows has an embedded firewall, linux has it as well, even a router has a firewall.

Because of this it seemed a faily good idea to give you some info about it. You never know when it might come in handy (like your trying to impress your lady…*ahem*).

A firewall is a piece of software which will protect your “environment” from abuse from an external source. Hackers for instance. It avoids external applications to reach your computer or your network. And most of the time this also works the other way around. It is very likely that your firewall will also prevent the applications on your computer to connect to the internet.

Don’t be alarmed you can configure your firewall in such a way that it allows exceptions for some programs.

There are different types of firewalls. And now you cannot stop reading yet because we’ll discuss all of them! Tremble in fear!

  1. Packet filtering firewall:
    As it may have become clear based on the name this is a firewall that works on the network level. Specifically on TCP/IP level. The firewall has a certain set of rules which determines if an IP package can or cannot pass.
  2. The application layer firewall:
    Another firewall which works on networklevel. This firewall works on the application layer (OSI model). For each existing protocol there is decided if packages can pass or not.
    This type of firewall will also protect from most virusses. A nice example of this type is a firewall that listens on the SMTP port of a mailserver.
  3. The Stateless Firewall:
    Another logical name for a logical explaination. It basically means that this firewall treats each and every package. This firewall does not store any information about connections which are open or used on the firewall. Which, apparently (I didn’t know either), has some disadvantages. So the better option would be the…
  4. Stateful Firewall:
    This firewall stores information about the open connections on the firewall. Like this a better or easier distinction can be made on which packages are allowed.

There is also a difference between personal firewalls and network firewalls. But I’m guessing I don’t need to explain the difference right ;-)…

If you have some questions (which seems plausible) drop me a mail or post a comment!

By the way this was my 100th post! yay me! :D


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