Why do files need protection (access control) by the operating system?

The need for files to be protected through access control by the operating system is multifaceted, as reflected in the correct answer, which encompasses various types of threats. Access control serves as a security mechanism that safeguards files from unauthorized access and modification.

Firstly, malicious users may attempt to access personal files of another user. This highlight the importance of controlling who can view or use specific data, ensuring individuals' privacy and preventing unauthorized exposure to sensitive information.

Secondly, the risk of malicious users modifying the files belonging to another user is significant. Unauthorized modifications can lead to data corruption, loss of integrity, or even the replacement of critical files with harmful content. Access controls must enforce restrictions that preserve not only privacy but also the integrity of users' data.

Lastly, there is the threat that malicious users might try to access and sell personal data belonging to another user. This situation underscores the need for strict access controls to prevent data breaches and the illicit exploitation of sensitive information for financial gain.

By encompassing all these scenarios, access control mechanisms implemented by the operating system are essential for protecting user data from a wide array of potential threats, ensuring that users can operate securely and maintain their privacy in digital environments.