Term Kind Topic What it is
Default Deny practice Firewalls & Security Groups A firewall posture in which nothing is permitted unless explicitly allowed, as opposed to blocking known-bad traffic.
Firewalls and Security Groups concept Firewalls & Security Groups Network-level access control, its real value as a second layer, and why the perimeter model stopped being sufficient.
Stateful Packet Filtering concept Firewalls & Security Groups Filtering that tracks connection state, so return traffic for an allowed outbound connection is permitted automatically.