A proxy server can filter internet access by controlling which websites or services users can reach. It enforces content policies and can provide caching and monitoring.

A. A router directs traffic but doesn’t filter internet sites by itself.

B. A cloud gateway could also filter, but the most direct answer is proxy.

D. An IDS detects suspicious activity but doesn’t filter browsing access.

References (CompTIA Network+ N10-009):

Domain: Network Security — Proxy servers, filtering, access control.