Question 839 of 976
hardMultiple ChoiceObjective-mapped
Bell-LaPadula MAC: Can a Secret Subject Read Confidential and Write to Top Secret?
In a MAC environment implementing Bell-LaPadula, a subject with Secret clearance attempts to read an object classified as Confidential and write to an object classified as Top Secret. Which operations are permitted?
Quick Answer
The answer is that both the read and write operations are permitted. This is correct because the Bell-LaPadula model enforces two core rules: the Simple Security Property prohibits reading up, meaning a Secret subject cannot read Top Secret, but reading down to Confidential is allowed; the *-Property prohibits writing down, so writing to Confidential would be blocked, but writing up to Top Secret is permitted. On the ISC2 Certified in Cybersecurity CC exam, this scenario tests your ability to apply mandatory access control rules to clearance levels, often appearing as a trick question where candidates mistakenly assume both operations are denied. A common trap is confusing the direction of the restrictions—remember that Bell-LaPadula focuses on preventing information flow from high to low, not low to high. For a quick memory tip, think “read down, write up” to recall that lower clearances can read below and write above.
⚠ Common exam trap
ISC2 often tests the misconception that both read and write must be at the same clearance level, but Bell-LaPadula actually allows reading down and writing up, not the reverse.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Both read and write allowed
In Bell-LaPadula, the Simple Security Property (no read up) prevents a subject from reading an object at a higher classification, but reading down is allowed. The *-Property (no write down) prevents writing to a lower classification, but writing up is allowed. Since the subject has Secret clearance, reading Confidential (lower) is permitted, and writing to Top Secret (higher) is permitted, so both operations are allowed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Read denied, write allowed
Why it's wrong here
Read of Confidential is allowed (read down).
- ✓
Both read and write allowed
Why this is correct
Both operations are permitted under Bell-LaPadula's mandatory access control principles. The subject, with Secret clearance, is allowed to read the Confidential object because this satisfies the Simple Security Property, which permits reading down to lower classifications. Concurrently, writing to the Top Secret object is permitted as it adheres to the \*-Property (Star Property), which allows writing up to higher classifications. This design ensures information only flows upwards, preventing unauthorised disclosure.
- ✗
Read allowed, write denied
Why it's wrong here
Write to Top Secret is allowed (write up).
- ✗
Both read and write denied
Why it's wrong here
Both operations are allowed.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
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Same concept, more angles
1 more way this is tested on CC
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. In a Bell-LaPadula MAC model, which of the following operations is prohibited?
hard- A.A Top Secret subject reads a Confidential object
- B.A Top Secret subject reads a Top Secret object
- C.A Top Secret subject writes to a Top Secret object
- ✓ D.A Top Secret subject writes to an Unclassified object
Why D: In the Bell-LaPadula model, the *-property (star property) prohibits a subject from writing to an object at a lower classification level. A Top Secret subject writing to an Unclassified object would cause a downgrade of sensitive information, violating this property. Therefore, option D is the prohibited operation.
Last reviewed: Jun 30, 2026
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