working with firewalls

[gib999]

Can comeone please explain to me what the exact definition of a firewall is? I have a vague idea of what it is, but something a little more precise would help. Specifically, in an office network, is it something that sits outside the router to the office network, on the router, between the router and the other computers, or is there one firewall on each computer in the network? How can I check to see if we have one running on our computers or network?

 

[Davetoo]

http://www.google.com/search?hl=en&q=firewall+definition

I'm Certifiable, not certified.
It just means my answers are from experience, not a book.

 

[zeveck]

Specifically, in an office network, is it something that sits outside the router to the office network, on the router, between the router and the other computers, or is there one firewall on each computer in the network? How can I check to see if we have one running on our computers or network?

Umm...it actually can be all of those things.

1. is it something that sits outside the router to the office network

This is a common setup and makes a lot of sense. Basically, your Internet connection comes in, hits the firewall, and then hits your router and goes wherever it has to on your internal network. This might be referred to as a "boundary firewall".

2. on the router

This is also fairly common, and is available even in home routers. Some routers claim to be a firewall because they support NAT, but that isn't quite the same as a "stateful firewall". Some routers have real firewalls. Depends on the router. This is effectively the same as 1.

3. between the router and the other computers

This makes sense when you need a DMZ. Here you'll let the Internet hit the router, have the router's firewall disabled, and then have a firewall protecting the ports off the router that lead to the internal network but have other computers connecting straight to the Internet.

4. is there one firewall on each computer in the network

This is called a personal firewall. I use Sygate Personal Firewall. Windows XP has a kinda crappy personal firewall built in. This often makes sense even if the network is behind a firewall because a firewall just protects the boundary and does nothing to protect internal computers from one another.