Firewalls

• A device that historically sits at the border between different networks and monitors traffic flowing between them.

• It’s capable of reading packet data and either allowing or denying traffic based on that data.

• Firewalls establish a barrier between networks of different security levels.

• What data a firewall can read and act on depends on the OSI layer the firewall operates on. For example: if it’s a L3 it can read and act towards source and destination IP addresses and ranges. L4 protocol and port numbers, L5 can act as a L4 also but understand response traffic, and L7 application specifics.