Which of the following ensures that data is not changed when it is not supposed to be?

The concept that ensures data is not changed when it is not supposed to be is integrity. Integrity in the context of data security refers to the accuracy and consistency of data over its entire lifecycle. This principle ensures that information remains unaltered during transmission or storage unless modifications are authorized and occur within the defined rules and policies.

Maintaining integrity involves implementing checks such as hash functions and digital signatures to verify that data remains intact and unmodified. When integrity is compromised, it can lead to unauthorized changes, which can result in misinformation, errors in processing, and potential security breaches.

The other concepts are important in their own right: confidentiality relates to ensuring that data is only accessible to authorized users, availability focuses on ensuring that information is accessible when needed, and accounting pertains to tracking and logging access to data and resources. However, it is the principle of integrity that directly addresses the need to prevent unauthorized changes to data.