What Does A Firewall Not Protect Against - D-Link DFL-1600 User Manual

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complies with current protocol definitions. This can prevent poorly
implemented services on the protected servers and client software from
being exposed to unexpected data, causing them to hang or crash. In short,
a firewall is the network's answer to poor host security.
3.2 What does a Firewall NOT protect
against?
Security means much more than just firewalls. However, in most cases,
installing a firewall is a necessary first step towards securing your network
and computers.
This section is not specifically devoted to D-Link firewalls; instead it
discusses firewalls in general. The problems described here will occur no
matter which firewall you choose to install.
A common misconception is that all communication is immediately made
safe and secure once it passes through a firewall. This is however not true.
Many marketing executives and sales people smile and claim that "our
firewall will protect you against everything". We hope that this is just
sheer ignorance on their part and not a conscious attempt to mislead
potential buyers.
A firewall can only protect against that for which it was designed.
Unfortunately, it is impossible to predict all the bugs other software may
have. In addition, there are a large number of situations where a firewall
quite simply cannot provide protection since not all communication passes
through it.
The following is a selection of security problems that firewalls are often
unable to deal with, and in some instances we have provided solutions to
combat these.
Please note that this only scratches the surface in terms of the number of
existing problems.
Complete protection can only be achieved through thorough understanding
of all possible weaknesses in network protocols and in the software used,
and by implementing appropriate measures to compensate for these.
D-Link Firewalls User's Guide
Chapter 3. Firewall Principles