SC-200 Perform threat hunting Practice Question
You are hunting for signs of ransomware using Microsoft Defender XDR's advanced hunting. Which query pattern would best identify a process that encrypts many files in a short time?
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
✓
DeviceFileEvents | where ActionType == 'FileModified' | summarize Count = count() by DeviceName, InitiatingProcessFileName, bin(Timestamp, 5m) | where Count > 100
It counts the number of file modifications per initiating process per 5-minute window using DeviceFileEvents, and then filters for those with more than 100 modifications. This directly detects a process that is rapidly encrypting many files, which is a strong indicator of ransomware. Option A is wrong because it measures the duration between the first and last file event by a process, not the count; a process could encrypt files over a longer period and still be suspicious, but this query would miss high-density encryption in a short burst. Option C is wrong because it only looks at process creation events for specific script interpreters (powershell.exe, wscript.exe), not at file modifications, and it fails to identify encryption activity from other executables. Option D is wrong because it counts all file events per device without grouping by process, so it cannot pinpoint which process is responsible for the encryption.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DeviceFileEvents | summarize Duration = max(Timestamp)-min(Timestamp) by DeviceName, InitiatingProcessFileName | where Duration < 1h
Why it's wrong here
This measures the elapsed time between a device's first and last file event, not the volume of files a single process encrypts. It is tempting because burst-timing analysis does surface ransomware, but the correct query aggregates file counts per InitiatingProcessFileName within a short window.
- ✓
DeviceFileEvents | where ActionType == 'FileModified' | summarize Count = count() by DeviceName, InitiatingProcessFileName, bin(Timestamp, 5m) | where Count > 100
Why this is correct
Aggregating DeviceFileEvents by device, initiating process and five-minute bins, then filtering counts above 100, directly surfaces mass file modification — the ransomware encryption signature. Grouping by InitiatingProcessFileName attributes the burst to a specific process, satisfying the stem's requirement to identify rapid, high-volume encryption activity.
- ✗
DeviceProcessEvents | where FileName in ('powershell.exe', 'wscript.exe') | summarize by DeviceName
Why it's wrong here
This shows script usage but not the encryption activity.
- ✗
DeviceFileEvents | summarize Count = count() by DeviceName | where Count > 1000
Why it's wrong here
Counting all file events per device ignores which process wrote them, so normal bulk activity triggers false positives and single-process encryption is missed. It is tempting because high file counts do suggest ransomware, but the correct query groups by InitiatingProcessFileName and applies a short time window.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SC-200 practice question is part of Courseiva's free Microsoft 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 SC-200 exam.