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ISC2 CC Practice Question: Which TWO of the following are fundamental…
Which TWO of the following are fundamental security principles? (Select TWO.)
⚠ Common exam trap
ISC2 often tests the distinction between security principles (like defense in depth and least privilege) and design concepts (like fail-open or complexity), so candidates mistakenly select 'fail-open' because it sounds security-related, but it actually reduces security in a failure scenario.
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
✓
Defense in depth
Defense in depth (C) is a fundamental security principle because it layers multiple independent controls (network, host, application, data) so that if one control fails, others still protect the asset. Least privilege (D) is also fundamental: users, processes, and services should be granted only the minimum access rights needed to perform their function, limiting the blast radius of compromise or misuse. The other options are not fundamental security principles: fail-open (A) is an availability-oriented failure mode that weakens security by allowing access when a control fails, need to share (B) is the opposite of the need-to-know principle, and complexity (E) is a known enemy of security that increases attack surface and misconfiguration risk.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Fail-open
Why it's wrong here
Fail-open lets a control default to permitting access when it malfunctions, so availability is preserved at the cost of enforcement; fundamental principles instead include fail-safe defaults and least privilege. It is tempting because fail-open suits life-safety or availability-critical systems where outage harm exceeds exposure.
- ✗
Need to share
Why it's wrong here
Need to share inverts the least-privilege and need-to-know principles, granting broad access by default rather than restricting it to justified recipients. It is tempting because collaboration and data availability genuinely require sharing, so the principle applies to business workflows, not to security design.
- ✓
Defense in depth
Why this is correct
Defense in depth is a fundamental security principle: it layers independent controls so failure of one does not expose the whole system. This satisfies the stem's requirement to select genuine fundamental principles, distinguishing it from specific technologies or implementation tactics.
- ✓
Least privilege
Why this is correct
Least privilege is a fundamental security principle: subjects receive only the minimum access needed for their tasks. This satisfies the stem's requirement to select genuine fundamental principles, distinguishing it from specific controls or products that merely implement the concept.
- ✗
Complexity
Why it's wrong here
Complexity is not a fundamental security principle; it actively undermines security by enlarging the attack surface and hiding flaws, whereas the recognised principles are confidentiality, integrity and availability. It is tempting because complex cryptographic algorithms and layered defences genuinely strengthen specific controls, so complexity can be a deliberate design tactic — but never a foundational principle in itself.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
Go deeper
Related to this question
Learn chapter
Network Security Foundations
Key term
Access control
Access control is the security practice of determining who or what is allowed to view, use, or enter a resource, and under what conditions.
Key term
Remote Authentication Dial-in User Service
RADIUS is a network protocol that provides centralized authentication, authorization, and accounting for users trying to connect to a network service.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CC practice question is part of Courseiva's free ISC2 certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CC exam.