What does the * (star) property mean in the Bell-LaPadula model?

A.
No write up

B.
No read up

C.
No write down

D.
No read down

Explanation:
Three main rules are used and enforced in the Bell-LaPadula model:
The simple security (SS) rule, the *-property (star property) rule, and the strong star property rule. The simple
security rule states that a subject at a given security level cannot read data that reside at a higher security level.
The *-property rule (star property rule) states that a subject in a given security level cannot write information to
a lower security level. The simple security rule is referred to as the “no read up” rule, and the *-property rule is
referred to as the “no write down”rule.
The third rule, the strong star property rule, states that a subject that has read and write capabilities can only
perform those functions at the same security level; nothing higher and nothing lower. So, for a subject to be
able to read and write to an object, the clearance and classification must be equal.
Incorrect Answers:
A: The *-property rule is referred to as the “no write down” rule, not the “no write up” rule.
B: The *-property rule is referred to as the “no write down” rule, not the “no read up” rule.
D: The *-property rule is referred to as the “no write down” rule, not the “no read down” rule.References:
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, pp. 369-370