Firewall packet filtering rules are applied based on the integrity of the networks. There are three types of the networks defined by the rule of the security perimeter and the trust of the firewall against the origin of the packet.
When a network is created by the network manager or the network administrator, it is classified under one of the three network types:
- Trusted network
- Untrusted network
- Unknown network
Let’s know about them one by one —
A trusted network is the one which is under the control of the network manager or the network administrator.
Basically, this is the network that a network admin tries to protect and defines the security parameters for the same. So, it can also be said that the trusted networks are within the security perimeter.
To monitor the outgoing as well as incoming traffic, we set up a firewall and define some rules for the bidirectional packets exchange on the firewall server. Once we do the initial configuration for the firewall, all the network behind the firewall lies within the trusted network.
Exception — Virtual private networks (VPNs)As far as VPNs are concerned, they transfer data across an untrusted network and still are counted as the trusted networks because the origination of the packet is within the trusted network.
As far as VPNs are concerned, they transfer data across an untrusted network and are still counted as the trusted networks because the origin of the packet is within the trusted network.
Untrusted networks are situated outside the security perimeter and control of the network admin. They could even be a private or a shared network.
When the firewall is configured, we initialize a rule and identify the untrusted networks from which the firewall can accept data requests.
Unknown networks are networks that are neither trusted nor untrusted. They are said to be unknown because firewall has no knowledge about those networks. Mathematically, Unknown networks are a subset of Untrusted networks.