What defines the role of measures in an information system's security?

The role of measures in an information system's security is primarily focused on ensuring data integrity and availability. When it is stated that measures ensure data remains available and unchanged, it refers to crucial security principles known as the CIA triad: confidentiality, integrity, and availability.

In this context, integrity means that the data is accurate and trustworthy, and availability means that authorized users have uninterrupted access to the data when needed. Measures might include implementing controls such as access permissions, encryption, regular backups, and system monitoring that ensure data does not get altered or lost unexpectedly. By maintaining the integrity and availability of data, these security measures help protect against unauthorized access and potential data breaches, thus securing the overall information system.

While restricting user access and monitoring system performance are important aspects of information security, they serve different functions within the broader security framework and do not encapsulate the holistic aim of safeguarding data integrity and availability as clearly as the correct answer does. Enhancing ease of use does not align with the primary objectives of security measures, which are fundamentally rooted in protecting sensitive information and ensuring its reliability for users.