Which of the following is NOT a toolset or technology commonly used to secure data?

Marking is not typically categorized as a toolset or technology focused on securing data like the other options provided. Instead, it refers to the process of labeling or identifying data for specific purposes, such as classification or management, which does not directly enhance its security.

In contrast, anonymization, masking, and encryption are widely recognized as techniques used to enhance data protection. Anonymization involves removing personally identifiable information to prevent tracing data back to an individual. Masking allows for sensitive data to be obscured or transformed so that unauthorized individuals cannot access the real information, while encryption involves converting data into a coded format that can only be accessed by those who possess the appropriate decryption key. All these methods are designed explicitly to secure data against unauthorized access or breaches, highlighting their role as security technologies, whereas marking serves a different and less protective function.