Security Concepts and Practices for SSCP

Sample Practice Questions

1. Question 1

   What does it mean to say that sensitivity labels are "incomparable"?
   1. A. The number of classification in the two labels is different.
   2. B. Neither label contains all the classifications of the other.
   3. C. the number of categories in the two labels are different.
   4. D. Neither label contains all the categories of the other.
   Explanation

   The correct answer is: D. Neither label contains all the categories of the other..

   Sensitivity labels are "incomparable" when neither label contains all the categories of the other — neither label dominates because each has at least one category the other lacks, even if their classification levels are identical. In a lattice, incomparable labels exist where dominance cannot be established. Saying the number of classifications differs misses the categorical aspect; classification is hierarchical while categories are non-hierarchical. Saying neither label contains all classifications of the other inverts the structure; classifications are hierarchical and one or the other dominates on that axis. Saying the number of categories differs is the wrong frame; incomparability is about set containment, not count. Bell-LaPadula and similar lattice models must handle incomparable labels carefully because no dominance ordering exists.

2. Question 2

   Who developed one of the first mathematical models of a multilevel-security computer system?
   1. A. Diffie and Hellman.
   2. B. Clark and Wilson.
   3. C. Bell and LaPadula.
   4. D. Gasser and Lipner.
   Explanation

   The correct answer is: C. Bell and LaPadula..

   Bell and LaPadula developed one of the first mathematical models of a multilevel-security computer system, formalising confidentiality with the simple-security and *-property rules over classification labels. The Bell-LaPadula model is the foundational MAC model. Diffie and Hellman invented public-key cryptography and the Diffie-Hellman key exchange; unrelated to access-control modelling. Clark and Wilson formulated the Clark-Wilson commercial integrity model later. Gasser and Lipner are figures in the broader security-architecture literature but did not create the foundational multilevel-security mathematical model. Bell-LaPadula remains the textbook example for formal confidentiality models.

3. Question 3

   Guards are appropriate whenever the function required by the security program involves which of the following?
   1. A. The use of discriminating judgment
   2. B. The use of physical force
   3. C. The operation of access control devices
   4. D. The need to detect unauthorized access
   Explanation

   The correct answer is: A. The use of discriminating judgment.

   Guards are appropriate whenever the security program involves the use of discriminating judgement — situations where a binary decision (allow/deny) is inadequate and human reasoning is needed to assess context, intent, and circumstance. Judgement is what humans add that machines cannot. The use of physical force may be necessary occasionally but is rare and is not the primary value guards add. The operation of access control devices can be done by automated card readers or biometric scanners; humans add little to routine card-reading. The need to detect unauthorised access can also be addressed by sensors and cameras; guards add value when those sensors require interpretation. Deploy guards in environments where contextual judgement adds value beyond what automation can provide.

4. Question 4

   Which is the last line of defense in a physical security sense?
   1. A. people
   2. B. interior barriers
   3. C. exterior barriers
   4. D. perimeter barriers
   Explanation

   The correct answer is: A. people.

   People are the last line of defense in physical security — guards, response teams, and aware employees are who handle situations when all the technical and structural barriers have been breached or bypassed. Human judgement, escalation, and physical response are irreplaceable. Interior barriers (walls, doors, locks) form the inner layers of physical defence but are not the ultimate fallback. Exterior barriers (fences, gates, perimeter) are the outermost layers; the first contact rather than the last. Perimeter barriers are the outermost layer of all; first to be tested by an attacker. Design physical security in concentric layers (perimeter → exterior → interior → people) so an intruder must defeat each one in sequence.

5. Question 5

   In which of the following security models is the subject's clearance compared to the object's classification such that specific rules can be applied to control how the subject-to-object interactions take place?
   1. A. Bell-LaPadula model
   2. B. Biba model
   3. C. Access Matrix model
   4. D. Take-Grant model
   Explanation

   The correct answer is: A. Bell-LaPadula model.

   The Bell-LaPadula model compares the subject's clearance to the object's classification and applies specific rules (no read up, no write down) to control subject-to-object interactions. Label-based comparison is the heart of Bell-LaPadula. The Biba model uses similar label comparisons but for integrity (no write up, no read down); different security property. The Access Matrix model represents permissions in a two-dimensional table but does not specifically use clearance-classification labels. The Take-Grant model is a graph-based formalism analysing how rights propagate through take and grant operations; not specifically clearance-classification. Bell-LaPadula is the foundational MAC model for government and military confidentiality enforcement.

Other SSCP domains

• Access Controls (203 questions)
• Cryptography (185 questions)
• Incident Response and Recovery (112 questions)
• Network and Communications Security (252 questions)
• Risk Identification, Monitoring, and Analysis (59 questions)
• Systems and Application Security (26 questions)