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SC-200 Practice Question: A SOC analyst is configuring an analytics rule in…
A SOC analyst is configuring an analytics rule in Microsoft Sentinel. The rule should run every hour and check for sign-ins from users who have been inactive for more than 30 days. The analyst uses the SigninLogs and IdentityInfo tables. Which KQL query pattern should be used to identify these users?
⚠ Common exam trap
Candidates often confuse `leftanti` with `rightanti` or `leftouter` joins, mistakenly thinking that summarizing sign-ins first and then joining will correctly identify inactive users, when in fact the direction of the anti-join determines which table's unmatched rows are returned.
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
✓
IdentityInfo | join kind=leftanti (SigninLogs | where TimeGenerated > ago(30d)) on UserPrincipalName
It uses a `leftanti` join to return all rows from the `IdentityInfo` table that have no matching `UserPrincipalName` in the `SigninLogs` table for the last 30 days. This directly identifies users who are in the identity inventory but have not signed in within the past 30 days, which is the exact requirement for detecting inactive users.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
union IdentityInfo, SigninLogs | where TimeGenerated > ago(30d) | summarize by UserPrincipalName
Why it's wrong here
This approach combines both tables and then filters for recent records, which would not identify users with no recent sign-ins.
- ✓
IdentityInfo | join kind=leftanti (SigninLogs | where TimeGenerated > ago(30d)) on UserPrincipalName
Why this is correct
Correct. The left anti join returns all rows from IdentityInfo that do not have a matching UserPrincipalName in the recent SigninLogs, effectively finding inactive users.
- ✗
SigninLogs | where TimeGenerated > ago(30d) | summarize by UserPrincipalName | join kind=rightanti IdentityInfo on UserPrincipalName
Why it's wrong here
This would return users in SigninLogs that are not in IdentityInfo, which is the opposite of what is needed.
- ✗
SigninLogs | where TimeGenerated < ago(30d) | summarize by UserPrincipalName
Why it's wrong here
This filters for sign-ins older than 30 days, which does not identify inactive users; it just returns historical sign-in records.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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