The term "attack surface" refers to the sum of all possible points where an unauthorized user can try to enter data to or extract data from an environment. The enabled USB ports on a laptop are considered a part of the physical attack surface because they allow for physical interaction with the device. This includes the potential for unauthorized devices to be connected, which could be used to compromise security, such as through the introduction of malware or the unauthorized copying of sensitive data.
References: This explanation aligns with the definitions provided in network security resources, which categorize attack surfaces based on the nature of the interaction-physical, network, or software12. The reference to the physical attack surface includes any physical means by which data can be compromised, which encompasses USB ports on a laptop1.