We saw on the previous pages how packet filtering works, however in the case of application/proxy filtering the processes are quite different. Using this method the firewall acts as a large storage device, or proxy (see proxy section). All of the computers on the protected side of the firewall make their internet requests to the proxy sever which in turn, through the firewall, retrieves the information. This method has the added advantage that none of the actual computer systems are connected directly to the internet, instead only the proxy server maintains a connection to the internet and therefore is capable of blocking/filter any unrequired data.
What Firewalls will not protect you from!
However much you may think they can do, firewalls can only do so much in protecting your computer system or network. Things the your firewall can't prevent are:
Software Bugs In the past there have been many “back doors” to your system which been known public. This only applies to bugs within software firewalls.
Human error Machines will do exactly what we tell them to do, as do firewalls. If a firewall is not configured to protect, it will not do so.
Viruses Once a virus has embedded itself onto your system, a firewall cannot and will not help you. However some firewalls do come with anti-virus software also.
Inside Jobs Be sure that you trust the right people with access to your network, there is no stopping a hacker with access.
