The network defense approach that was employed by Alice on her laptop was the preventive approach. The preventive approach aims to stop or deter potential attacks before they happen by implementing security measures that reduce the attack surface and increase the difficulty of exploitation. Biometric authentication is an example of a preventive measure that uses a physical characteristic, such as a fingerprint, iris, or face, to verify the identity of the user and grant access to the device or system. Biometric authentication is more secure than traditional methods, such as passwords or PINs, because it is harder to forge, guess, or steal. By locking her laptop and using biometric authentication, Alice prevented Bob from accessing her laptop and her confidential files without her permission.References:

Network Defense Essentials Courseware, EC-Council, 2020, pp. 1-7 to 1-8

What is Biometric Authentication?, Norton, July 29, 2020

An introduction to network defense basics, Enable Sysadmin, November 26, 2019