A computer firewalls act as a barrier between computers on a network. It protect inside networks from unauthorized access by users on an outside network and protect inside networks from each other.
Why we need a VPN Firewall?
Without a firewall, intruders/hacker on the network would likely be able to destroy, tamper with or gain access to the files on your computer. With a firewall, you block all traffic to your box, except for the traffic you initiate.
How it Works?
Firewalls function with a set of filters that are continuously monitoring traffic on the network. Whenever a packet of information triggers one of the filters, the firewall prevents it from passing through to prevent any unwanted damages. Of course, Firewalls sometimes block wanted traffic, and through a continual process of refinement, the filters can be customized to improve their efficacy.
Controlling network resources to an outside user
If you have network resources that need to be available to an outside user, such as a web or FTP server, you can place a demilitarized zone (DMZ) on a separate network behind the firewall. The firewall allows limited access to the DMZ, but because the DMZ only includes the public servers, an attack there only affects the servers and does not affect the other inside networks.
Controlling inside users accessing outside network
You may also control inside users access outside networks,
- by allowing only certain addresses out,
- by requiring authentication or authorization, or
- by coordinating with an external URL filtering server.