What mechanism does the Linux operating system provide to control access to files?

'Privileges required' is a metric in the CVSS vulnerability scoring system used to rate exploit difficulty, not a Linux access control mechanism.

'User interaction' is a CVSS scoring metric describing whether a user must participate for a vulnerability to be exploited, unrelated to Linux file access.

Linux uses a file permissions system where each file and directory has three permission sets - owner, group, and others - each with read (r), write (w), and execute (x) flags enforced by the kernel. Commands such as chmod and chown are used to modify these permissions. This is the primary discretionary access control mechanism provided by the Linux operating system.

'Access complexity' is a CVSS v2 metric for rating vulnerability exploitability and has no role in Linux file access control.