Discretionary Access Control (DAC)

Under Discretionary Access Control, the resource owner decides. Create a file and you can grant read, write, or execute to whomever you choose, and you can pass that granting power along. It is the model behind ordinary file permissions in Windows and Unix, and its strength is flexibility: access decisions sit with the people closest to the data rather than a central authority.

That flexibility is also its weakness. Because owners can propagate rights freely, permissions drift, and a single compromised or careless user can widen access far beyond intent. This is the exact opposite trade-off from mandatory access control, where a central policy overrides owners entirely. The granting and transferring of rights that DAC relies on is formalised in the Graham-Denning model, and disciplined DAC still depends on least privilege to keep grants minimal.

Exam relevance: the identifying phrase is “the owner determines access”. If users can share their own files at will, it is DAC. Contrast it against MAC (system-enforced labels) and role-based access control (permissions attached to job roles); the exam frequently lines all three up and asks which fits a described organisation.