Final answer:
User authentication and Instance restriction are examples of contextual security, which adapts security measures based on specific situations such as user identity, location, and device. Contextual security is distinct from physical security and platform access.
Step-by-step explanation:
User authentication and Instance restriction are examples of contextual security, which refers to the implementation of security measures that are tailored to specific contexts or situations. This encompasses a range of strategies designed to protect data, applications, and infrastructure based on the context in which they are accessed or used.
Contextual security often involves analyzing various factors such as the user's identity, location, the device being used, and the time of access to determine the appropriate level of security required. For example, user authentication requires proof of identity, whereas instance restriction limits the accessibility of a system to particular instances or scenarios.
These measures contrast with other types of security such as physical security, which concerns tangible protections like locks and surveillance systems, or platform access which strictly controls access to specific platforms or applications through predefined permissions.