What is the purpose of Ingress Filtering?

• A. A method of filtering inbound network traffic such that only explicitly allowed traffic is permitted to enter the network.
• B. Blocking outbound traffic only.
• C. Encrypting inbound traffic.
• D. Logging all inbound traffic without filtering.

Answer: (A)

Ingress filtering focuses on controlling what can enter a network by applying a policy to inbound traffic. It uses an allowlist approach: only traffic that has been explicitly permitted is allowed to pass into the network, while everything else is blocked or denied by default. This tightens the entry points to your systems and reduces the chances that harmful or unauthorized traffic can reach internal resources.

This is different from blocking outbound traffic (that’s egress filtering), encrypting inbound traffic (that’s about confidentiality, not filtering), or logging inbound traffic without applying any access restrictions (which leaves the network open to whatever arrives). In practice, you implement ingress filtering with firewalls or access control lists to permit necessary services from trusted sources and deny everything else, often adopting a default-deny posture to strengthen boundary protection.