A breach at a government agency resulted in the public release of top secret information. The Chief Information Security Officer has tasked a group of security professionals to deploy a system which…

DAC cannot enforce no read-up and no write-down in a mandatory sense because DAC allows resource owners to grant permissions discretionarily, undermining strict classification enforcement.

No write-up and no read-down are the properties of the Biba integrity model, which protects data integrity rather than confidentiality, and would not prevent top secret data from being read by lower-clearance subjects.

The Bell-LaPadula model uses MAC to enforce two core rules: the Simple Security Property (no read-up) prevents subjects from reading objects classified above their clearance level, and the Star Property (no write-down) prevents subjects from writing data to objects at a lower classification, which would leak sensitive information. Combining these two MAC controls with DAC for discretionary access within classification levels provides a comprehensive confidentiality model appropriate for government top secret data. This combination directly addresses the breach by blocking both unauthorized reads and downward data leakage.

DAC cannot enforce no write-up and no read-down in a mandatory classification hierarchy; DAC is discretionary and does not enforce mandatory labels across all subjects.