Using KQL to Detect Brute-Force Attacks on Microsoft Teams in Sentinel
This SC-900 practice question tests your understanding of describe the capabilities of microsoft security solutions. 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.
Exhibit
Refer to the exhibit.
```kql
// Microsoft Sentinel KQL query
let timeframe = 7d;
IdentityLogonEvents
| where Timestamp > ago(timeframe)
| where Application == "Microsoft Teams"
| summarize LogonAttempts = count() by UserPrincipalName, IPAddress
| where LogonAttempts > 10
| join kind=inner (
AADNonInteractiveUserSignInLogs
| where Timestamp > ago(timeframe)
| summarize FailedSignIns = count() by UserPrincipalName
) on UserPrincipalName
| project UserPrincipalName, IPAddress, LogonAttempts, FailedSignIns
| order by FailedSignIns desc
```
You are reviewing a Microsoft Sentinel KQL query. What is the primary purpose of this query?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Exhibit
Refer to the exhibit.
```kql
// Microsoft Sentinel KQL query
let timeframe = 7d;
IdentityLogonEvents
| where Timestamp > ago(timeframe)
| where Application == "Microsoft Teams"
| summarize LogonAttempts = count() by UserPrincipalName, IPAddress
| where LogonAttempts > 10
| join kind=inner (
AADNonInteractiveUserSignInLogs
| where Timestamp > ago(timeframe)
| summarize FailedSignIns = count() by UserPrincipalName
) on UserPrincipalName
| project UserPrincipalName, IPAddress, LogonAttempts, FailedSignIns
| order by FailedSignIns desc
```
A
Identify all users who have attempted to log on to Microsoft Teams more than 10 times in the last 7 days and who are global administrators
Why wrong: The query does not filter by admin roles.
B
Identify users with high logon attempts to Teams and high failed sign-ins, possibly indicating a brute-force attack
The query correlates high Teams logon attempts with high failed sign-ins, a common brute-force indicator.
C
Identify users with high failed sign-ins and check if they have conditional access policies applied
Why wrong: The query does not include conditional access data.
D
Identify users with high successful logon attempts to Teams and correlate with failed sign-ins to detect account compromise
Why wrong: The query counts all logon attempts, not just successful ones.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Identify users with high logon attempts to Teams and high failed sign-ins, possibly indicating a brute-force attack
The KQL query is designed to detect potential brute-force attacks by identifying users with both a high number of logon attempts to Microsoft Teams and a high number of failed sign-ins. This combination is a classic indicator of an automated password guessing attack, where an attacker tries many passwords against a single account. Option B correctly captures this threat detection purpose.
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.
✗
Identify all users who have attempted to log on to Microsoft Teams more than 10 times in the last 7 days and who are global administrators
Why it's wrong here
The query does not filter by admin roles.
✓
Identify users with high logon attempts to Teams and high failed sign-ins, possibly indicating a brute-force attack
Why this is correct
The query correlates high Teams logon attempts with high failed sign-ins, a common brute-force indicator.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Identify users with high failed sign-ins and check if they have conditional access policies applied
Why it's wrong here
The query does not include conditional access data.
✗
Identify users with high successful logon attempts to Teams and correlate with failed sign-ins to detect account compromise
Why it's wrong here
The query counts all logon attempts, not just successful ones.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the purpose of detecting a brute-force attack (high failed attempts) with detecting account compromise (high successful attempts followed by anomalies), leading them to choose option D instead of B.
Detailed technical explanation
How to think about this question
Under the hood, the KQL query likely uses the `SigninLogs` table, filtering for `AppId == 'c48b35f1-f6aa-48db-8a6d-8eec75d91d2b'` (Microsoft Teams) and aggregating by `UserPrincipalName` with `summarize` to count total logon attempts and failed sign-ins (where `ResultType != 0`). A brute-force attack is characterized by a high ratio of failures to total attempts, often exceeding 90%, which the query identifies without needing a fixed threshold. In real-world scenarios, this query helps SOC analysts prioritize accounts under active attack before the attacker succeeds.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-900 question in full detail.
Describe the capabilities of Microsoft security solutions — This question tests Describe the capabilities of Microsoft security solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Identify users with high logon attempts to Teams and high failed sign-ins, possibly indicating a brute-force attack — The KQL query is designed to detect potential brute-force attacks by identifying users with both a high number of logon attempts to Microsoft Teams and a high number of failed sign-ins. This combination is a classic indicator of an automated password guessing attack, where an attacker tries many passwords against a single account. Option B correctly captures this threat detection purpose.
What should I do if I get this SC-900 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: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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