Quick Answer
The correct answer is threat modeling, as it is the key activity during the design phase of the secure software development lifecycle (SSDLC). This is because threat modeling proactively identifies potential security threats, vulnerabilities, and attack vectors by analyzing system architecture, data flows, and trust boundaries before any code is written, allowing teams to embed security controls early and reduce costly fixes later. On the CISSP exam, this concept tests your understanding of the SSDLC’s design phase within Domain 8 (Software Development Security), often appearing in scenario-based questions where you must distinguish threat modeling from activities like code review (testing phase) or security requirements (initiation phase). A common trap is confusing threat modeling with vulnerability scanning, but remember: threat modeling is a design-time, proactive analysis, not a runtime tool. A useful memory tip is to associate the design phase with the mnemonic “STRIDE” (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege), which is a core threat modeling methodology you will apply on the exam.
This CISSP practice question tests your understanding of security architecture and engineering. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is implementing a secure software development lifecycle (SSDLC). Which of the following is a key activity during the design phase?
Static code analysis
Why wrong: Incorrect. Static analysis is performed on source code during development.
Code signing
Why wrong: Incorrect. Code signing is done during the build process.
Threat modeling
Correct. Threat modeling identifies threats and vulnerabilities early in the design phase.
Penetration testing
Why wrong: Incorrect. Penetration testing is performed on a running system.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Threat modeling
Threat modeling is a key activity during the design phase of the SSDLC because it proactively identifies potential security threats, vulnerabilities, and attack vectors before any code is written. By analyzing the system's architecture, data flows, and trust boundaries (e.g., using STRIDE or PASTA methodologies), teams can design security controls directly into the system, reducing the cost and impact of fixes later. This aligns with the NIST SP 800-64 and Microsoft SDL frameworks, which mandate threat modeling as a core design-phase activity.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Static code analysis
Why it's wrong here
Incorrect. Static analysis is performed on source code during development.
Code signing
Why it's wrong here
Incorrect. Code signing is done during the build process.
Threat modeling
Why this is correct
Correct. Threat modeling identifies threats and vulnerabilities early in the design phase.
Related concept
Read the scenario before looking for a memorised answer.
Penetration testing
Why it's wrong here
Incorrect. Penetration testing is performed on a running system.
Common exam traps
The trap here is that candidates confuse 'design phase' with 'implementation phase' activities, mistakenly selecting static code analysis (A) because it is a common security review, but it requires code to exist, whereas threat modeling is the only design-phase option that addresses architecture before code is written.
Detailed technical explanation
Threat modeling typically uses data flow diagrams (DFDs) to map trust boundaries and identify threats via frameworks like STRIDE (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege). For example, in a web application, a DFD might reveal that user input crosses a trust boundary into a database, prompting a STRIDE analysis to identify SQL injection as a Tampering threat, leading to parameterized queries as a design control. Real-world scenarios like the 2017 Equifax breach could have been mitigated by threat modeling that identified unpatched Apache Struts vulnerabilities as a design risk.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Security Architecture and Engineering — This question tests Security Architecture and Engineering — Read the scenario before looking for a memorised answer..
The correct answer is: Threat modeling — Threat modeling is a key activity during the design phase of the SSDLC because it proactively identifies potential security threats, vulnerabilities, and attack vectors before any code is written. By analyzing the system's architecture, data flows, and trust boundaries (e.g., using STRIDE or PASTA methodologies), teams can design security controls directly into the system, reducing the cost and impact of fixes later. This aligns with the NIST SP 800-64 and Microsoft SDL frameworks, which mandate threat modeling as a core design-phase activity.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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