This MS-900 practice question tests your understanding of describe microsoft 365 apps and services. 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 uses Microsoft 365 E5. The security team wants to automatically investigate and remediate advanced threats across email, endpoints, and identities. Which Microsoft 365 Defender workload should they enable?
Microsoft Defender for Identity
Why wrong: Incorrect. This only covers on-premises identities.
Microsoft Defender for Endpoint
Why wrong: Incorrect. This only covers endpoints.
Microsoft Defender for Office 365
Why wrong: Incorrect. This only covers email and collaboration.
Microsoft Defender XDR
Correct. XDR provides cross-domain investigation and response.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Microsoft Defender XDR
Microsoft Defender XDR (option D) is the correct answer because it is the unified, cross-domain security solution that correlates signals across email, endpoints, identities, and cloud apps to automatically investigate and remediate advanced threats. Unlike the individual Defender workloads, Defender XDR provides integrated incident response and automated actions across all these domains, which directly matches the requirement for automatic investigation and remediation across email, endpoints, and identities.
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.
Microsoft Defender for Identity
Why it's wrong here
Incorrect. This only covers on-premises identities.
Microsoft Defender for Endpoint
Why it's wrong here
Incorrect. This only covers endpoints.
Microsoft Defender for Office 365
Why it's wrong here
Incorrect. This only covers email and collaboration.
Microsoft Defender XDR
Why this is correct
Correct. XDR provides cross-domain investigation and response.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse the individual Defender workloads (Identity, Endpoint, Office 365) with the integrated cross-domain solution (Defender XDR), mistakenly thinking one of the single-domain tools can automatically investigate and remediate across all three domains simultaneously.
Detailed technical explanation
Under the hood, Microsoft Defender XDR uses a shared data lake and the Microsoft 365 Defender portal to correlate alerts from Defender for Identity, Defender for Endpoint, Defender for Office 365, and Defender for Cloud Apps into a single incident. Automated investigation and remediation (AIR) playbooks can then execute cross-domain actions, such as isolating a compromised endpoint while simultaneously resetting a user's password and removing malicious email, all triggered by a single alert. This unified approach reduces mean time to respond (MTTR) and prevents attackers from pivoting between domains.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
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FAQ
Describe Microsoft 365 apps and services — This question tests Describe Microsoft 365 apps and services — Read the scenario before looking for a memorised answer..
The correct answer is: Microsoft Defender XDR — Microsoft Defender XDR (option D) is the correct answer because it is the unified, cross-domain security solution that correlates signals across email, endpoints, identities, and cloud apps to automatically investigate and remediate advanced threats. Unlike the individual Defender workloads, Defender XDR provides integrated incident response and automated actions across all these domains, which directly matches the requirement for automatic investigation and remediation across email, endpoints, and identities.
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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