The (star) Property in the Bell-LaPadula Model

C.

The(star) property of the Bell-LaPadula access control model states that writing of information by a subject at a higher level of sensitivity to an object at a lower level of sensitivity is not permitted (no write down)

Source: KRUTZ, Ronald L.

& VINES, Russel.

D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, John Wiley & Sons, 2001, Chapter 5: Security Architectures and Models (page 202)

Also check out: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, McGraw-Hill/Osborne, 2002, Chapter 5: Security Models and Architecture (page 242, 243).

In the Bell-LaPadula model, the (star) property refers to the *-property, which is also known as the "star property" or the "tranquility property." It is one of the fundamental security properties of the model.

The *-property states that a subject at a particular security level cannot write to an object at a lower security level. This means that information cannot flow from a higher security level to a lower security level.

For example, suppose a user has a top-secret clearance and wants to write a document that contains top-secret information to a file that is classified as confidential. The *-property would prevent the user from doing so, as the user's security level is higher than the file's security level.

The *-property is important in enforcing confidentiality in the Bell-LaPadula model. By preventing information from flowing from higher security levels to lower security levels, it helps ensure that sensitive information is not leaked or compromised.

Therefore, option C "No write down" is the correct answer to the question.