Final answer:
Confidentiality is the fundamental tenet of information security that ensures sensitive information is protected from unauthorized access.
Step-by-step explanation:
The fundamental tenet of information security that ensures sensitive information is protected from unauthorized access is confidentiality. Confidentiality involves restricting access to information and ensuring that it is not viewed or processed by unauthorized persons, computers, or applications. This is typically achieved through the use of encryption, access controls, and other security measures.