Firewalls
A firewall is a system or group of systems that enforces an access control policy between two networks. Because it is a mechanism for
enforcing policy, it imposes its policy on everything behind it. Firewalls can be configured to protect against unauthenticated
logins from the remote devices, and still permit local users to communicate across the internet freely.
Software firewalls usually work by filtering or blocking information to individual programs and are often integrated with antivirus software while hardware firewalls filter traffic before it reaches your computer and may be integrated within your router or exist as a stand-alone unit.
By default, a firewall blocks all network traffic coming in to the network it is protecting. To permit traffic through the firewall, exceptions (or rules) are created that allow certain traffic on the network. The rules are defined by the domain names or IP addresses of the sender and receiver of the traffic as well as the type of traffic (e.g. web or SSH).
