Which statement best describes how ACLs function within a firewall?

• A. ACLs are used to encrypt traffic across networks.
• B. ACLs specify which packets or connections are allowed or denied based on attributes like IP, port, or protocol.
• C. ACLs route traffic between subnets.
• D. ACLs monitor network performance metrics.

Answer: (B)

ACLs in a firewall act as gatekeepers that decide which traffic is allowed or denied by inspecting attributes such as IP address, port, and protocol. This focus on specific packet or connection characteristics is why the description emphasizing allowed or denied traffic based on those attributes is the best fit. ACLs don’t encrypt data, don’t route traffic between subnets, and don’t monitor performance metrics—those are encryption, routing, and monitoring functions, respectively. For context, ACLs can be standard (filter by source IP) or extended (filter by source and destination IP, plus protocol and ports), and they’re typically evaluated in order with an implicit deny at the end.