CompTIA Network+

Answer: B - Using the ACL on the firewall to block already known websites describes IP Filtering.

Key Takeaway: ACLs, or Access Control Lists can be used to control access via IP addresses, MAC addresses, FQDNs, and others, in this case, we know that we are blocking websites that are already known. Our first option doesn’t work as web sites don’t have MAC addresses to block. If we had used port filtering, then not just the malicious websites would be blocked, all websites using the blocked ports would be. Finally packet filtering in this sense would accomplish the same goal, however the more plausible and realistic option is IP filtering since we know the IP addresses of the websites we want to block.