As soon as a computer is connected to the network, all kinds of
abuse becomes possible, be it a UNIX-based or any other system.
Admittedly, mountains of papers have been spilled on this subject
and it would lead us too far to discuss the subject of security in
detail. There are, however, a couple of fairly logical things even
a novice user can do to obtain a very secure system, because most
break-ins are the result of ignorant or careless users.
Maybe you are asking yourself if this all applies to you, using
your computer at home or working at your office on a desktop in a
fairly protected environment. The questions you should be asking
yourself, however, are more on the lines of:
Do you want to be in control of your own system?
Do you want to (unwittingly) participate in criminal
Do you want your equipment to be used by someone else?
Do you want to take risks on losing your Internet
Do you want to rebuild your system every time it has been
Do you want to risk personal or other data loss?
Presuming you don't, we will quickly list the steps you can take
to secure your machine. Extended information can be found in the
Linux Security HOWTO.