Internet
Firewalls
Jump to information links (below)
A firewall is basically a device or software configuration that decides
whether to allow certain communications through a connection or not.
It's primary purpose is to restrict access to computers or pathways
from remote and unknown computers and people.
A firewall is the first step in securing your Internet system.
The Internet communicates via a protocol
called TCP/IP.
TCP/IP operates on a system of ports where each standard
protocol uses a particular port number to initiate and control
a communication between computers.
TCP/IP communications work by sending a packet of information
that along with a payload of data includes addressing information
so the packet knows where it is going to and where it came from. It
is this information that can be checked by a system and that system
can determine if the packet should be allowed in, bounced back to
the sender with an error or discarded completely. This is the fundemental
process of an IP Filtering Firewall. Of course, it gets
quite a bit more complex than this and I'll leave it as an excersise
for the reader to investigate the complexity in their own time.
When constructing a firewall, you normally deny all access completely
from the outside world and then open only the ports you need in order
to operate the service you wish.
The security on a firewall is only as good as the ports you leave
open and the services listening on those ports
Links to further information on Firewalls
None currently listed.
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