The answer is to isolate the affected device from the network immediately. This is the correct first action because ransomware spreads laterally by exploiting protocols like SMB and RDP, and isolating the device in Microsoft Defender XDR blocks all inbound and outbound communication except with the Defender for Endpoint cloud service, halting the spread while preserving the device’s forensic state for investigation. On the MS-102 exam, this scenario tests your understanding of incident response priorities—specifically that containment must come before eradication or recovery. A common trap is choosing to run a full antivirus scan first, but scanning can alert the ransomware and trigger destructive encryption, whereas isolation buys time. Remember the memory tip: “Isolate before you eradicate” to lock down the threat before touching the system.
MS-102 Practice Question: Manage security and threats by using Microsoft Defender XDR
This MS-102 practice question tests your understanding of manage security and threats by using microsoft defender xdr. 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 ransomware alert is confirmed in Microsoft Defender XDR on a user device that is still communicating with other endpoints. What should the administrator do first to reduce spread while preserving the ability to investigate?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Isolate the affected device from the network
Option A is correct because immediately isolating the affected device from the network stops the ransomware from spreading laterally to other endpoints via SMB, RDP, or other protocols, while preserving the device's state for forensic analysis. Microsoft Defender XDR's device isolation feature blocks all inbound and outbound communication except with the Defender for Endpoint cloud service, allowing investigation to continue without the risk of further infection.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Isolate the affected device from the network
Why this is correct
Device isolation contains the threat quickly while retaining management connectivity for investigation and remediation.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Collect a forensic package before taking containment action
Why it's wrong here
Forensic collection is useful, but delaying containment can allow ransomware to spread to additional devices.
✗
Run a full antivirus scan before isolating the device
Why it's wrong here
Scanning may take time and does not immediately prevent lateral movement or additional network communication.
✗
Wait for automated investigation to complete before responding
Why it's wrong here
Automated investigation helps triage and remediate, but confirmed active ransomware requires immediate containment.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think they must preserve evidence first (Option B) or let automation run (Option D), but Microsoft explicitly prioritizes containment over collection in active ransomware outbreaks to prevent lateral spread.
Detailed technical explanation
How to think about this question
Device isolation in Microsoft Defender XDR works by applying a Windows Filtering Platform (WFP) firewall rule that blocks all traffic except traffic to the Defender cloud service (using specific IP ranges and ports 443/80) and local loopback. This ensures the device can still send telemetry and receive remediation commands while being cut off from the rest of the network. In a real-world scenario, an administrator might also use 'selective isolation' to allow only specific management tools, but full isolation is the default for confirmed ransomware.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this MS-102 question in full detail.
Manage security and threats by using Microsoft Defender XDR — This question tests Manage security and threats by using Microsoft Defender XDR — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Isolate the affected device from the network — Option A is correct because immediately isolating the affected device from the network stops the ransomware from spreading laterally to other endpoints via SMB, RDP, or other protocols, while preserving the device's state for forensic analysis. Microsoft Defender XDR's device isolation feature blocks all inbound and outbound communication except with the Defender for Endpoint cloud service, allowing investigation to continue without the risk of further infection.
What should I do if I get this MS-102 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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