KQL Query to Detect Brute Force Attacks: Aggregating Failed Logons
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
{
"exhibit": "Refer to the exhibit. The following is a KQL query run in Microsoft Sentinel: \nSecurityEvent | where TimeGenerated > ago(7d) | where EventID == 4625 | summarize FailedLogins = count() by Account, Computer | where FailedLogins > 10 | project Account, Computer, FailedLogins | sort by FailedLogins desc"
}
Refer to the exhibit. A security analyst runs this KQL query in Microsoft Sentinel. What is the most likely 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: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Exhibit
{
"exhibit": "Refer to the exhibit. The following is a KQL query run in Microsoft Sentinel: \nSecurityEvent | where TimeGenerated > ago(7d) | where EventID == 4625 | summarize FailedLogins = count() by Account, Computer | where FailedLogins > 10 | project Account, Computer, FailedLogins | sort by FailedLogins desc"
}
A
To identify successful logins after multiple failures
Why wrong: The query only counts failed logins, not successful ones.
B
To detect privilege escalation events
Why wrong: Privilege escalation events have different EventIDs (e.g., 4672).
C
To detect accounts that have been locked out
Why wrong: Account lockouts have a different EventID; this query focuses on failed logins.
D
To identify potential brute-force attack attempts
High number of failed logins from a single account is a common sign of brute-force attacks.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
To identify potential brute-force attack attempts
The query filters for Windows Event ID 4625 (failed logon) and then counts occurrences per account and source IP within a 5-minute window, keeping only those with more than 10 failures. This pattern is the classic signature of a brute-force attack, where an attacker attempts many passwords against the same account or from the same IP. Option D is correct because the query is specifically designed to identify potential brute-force attempts by aggregating failed logons.
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.
✗
To identify successful logins after multiple failures
Why it's wrong here
The query only counts failed logins, not successful ones.
✗
To detect privilege escalation events
Why it's wrong here
Privilege escalation events have different EventIDs (e.g., 4672).
✗
To detect accounts that have been locked out
Why it's wrong here
Account lockouts have a different EventID; this query focuses on failed logins.
✓
To identify potential brute-force attack attempts
Why this is correct
High number of failed logins from a single account is a common sign of brute-force attacks.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the aggregation of failed logons (Event ID 4625) with account lockout events (Event ID 4740), but the query lacks any reference to lockout status or successful logins, making brute-force detection the only logical purpose.
Detailed technical explanation
How to think about this question
Under the hood, Windows Security Log Event ID 4625 contains fields such as Account Name, Workstation Name, Source Network Address, and Status (e.g., 0xC000006A for incorrect password). By grouping on Account and IpAddress and applying a threshold (count > 10) within a short time window (5m), the query effectively implements a time-based sliding window anomaly detection for brute-force activity. In real-world scenarios, this query can be tuned to reduce false positives by excluding known service accounts or trusted IP ranges.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
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: To identify potential brute-force attack attempts — The query filters for Windows Event ID 4625 (failed logon) and then counts occurrences per account and source IP within a 5-minute window, keeping only those with more than 10 failures. This pattern is the classic signature of a brute-force attack, where an attacker attempts many passwords against the same account or from the same IP. Option D is correct because the query is specifically designed to identify potential brute-force attempts by aggregating failed logons.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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