When your computer is connected to the Internet, it is constantly exposed to
threats of hackers and viruses. Each day, several new viruses are released
to the Internet, and each day several new security vulnerabilities are
discovered - vulnerabilities that could potentially be used by hackers
trying to take over your computer or your network.
If you have a firewall
and an anti-virus scanner installed you have some protection against these
threats, but you protection is far from complete.
A firewall will only protect
your computer against certain specific
threats. It will not protect you when you are surfing the net or when you
receive e-mail. If you have a web server or an e-mail server, it will not
protect you against many types of vulnerabilities in the server program
that could be exploited by hackers.
An anti-virus scanner only protects you against known viruses.
Whenever a new virus is released, your anti-virus scanner has to be
updated to protect against it. No matter how often you update your
anti-virus scanner's virus definitions, there will always be viruses out
there, against which it won't yet protect you.