What security feature was introduced in DOCSIS 1.1 to combat modem cloning?

The security feature introduced in DOCSIS 1.1 to combat modem cloning is the Baseline Privacy Interface (BPI). This feature was implemented to ensure that the communications between the modem and the cable network are secure and that the legitimate devices are authenticated before they can access the network.

The BPI establishes a mechanism for encrypting the data and provides an authentication framework that helps prevent unauthorized access and reduces the risk of cloning. By securing the initialization process and protecting sensitive data transmitted over the network, BPI plays a crucial role in maintaining the integrity of the cable modem provisioning and thereby prevents instances of modem cloning, where unauthorized devices could potentially gain access to service without paying.

In contrast, other options such as enhanced encryption layers, firewall protection protocols, and Access Control Lists (ACLs) do not specifically address the modem authentication and initialization security that BPI provides. While they may play roles in broader security strategies, they are not the targeted solution for combating modem cloning as implemented by DOCSIS 1.1.