The correct answer is a brute force attack from a single source IP. This SIEM correlation rule is designed to detect this behavior by aggregating failed login attempts from one IP address within a defined time window—for example, ten failures in five minutes—and triggering an alert once the threshold is exceeded. This pattern directly maps to a brute force attack, where an adversary systematically tries numerous passwords against a single account or a small set of accounts from the same origin, distinguishing it from distributed or password-spraying attacks. On the CISSP exam, this concept tests your understanding of detection and response controls within the Security Operations domain; a common trap is confusing this rule with a distributed denial-of-service (DDoS) or credential stuffing attack, which involve multiple sources. Remember the mnemonic “One IP, Many Tries” to recall that a single-source brute force is the classic signature this correlation rule catches.
CISSP Security and Risk Management Practice Question
This CISSP practice question tests your understanding of security and risk management. 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.
SIEM Correlation Rule:
rule BruteForceDetection
{
meta:
description = "Detect multiple failed logins from same source"
strings:
$loginFailed = "Authentication failed" nocase
condition:
#loginFailed > 5 within 120 seconds
}
Based on the SIEM correlation rule, what behavior is this rule designed to detect?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Brute force attack from a single source IP
The SIEM correlation rule counts failed login attempts from a single source IP within a defined time window (e.g., 10 failures in 5 minutes). When the threshold is exceeded, it triggers an alert. This pattern is characteristic of a brute force attack, where an attacker tries many passwords against one account or a few accounts from the same IP address.
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.
✗
Account lockout due to excessive failures
Why it's wrong here
The rule does not check account lockout status; it only alerts on failure count.
✗
Successful login after multiple retries
Why it's wrong here
The rule only triggers on failed attempts, not successful logins.
✓
Brute force attack from a single source IP
Why this is correct
The condition detects >5 failed logins within 120 seconds from a single source, indicating a brute force attempt.
Related concept
Read the scenario before looking for a memorised answer.
✗
Password spraying attack against multiple accounts
Why it's wrong here
Password spraying typically uses a few passwords across many accounts; this rule counts many failures from one source.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the high-volume, single-source pattern of a brute force attack with the low-volume, multi-account pattern of a password spray, leading them to select option D.
Detailed technical explanation
How to think about this question
Under the hood, SIEM correlation rules often use a sliding time window (e.g., 5 minutes) and count events like Windows Event ID 4625 (failed logon). A brute force attack from a single source IP will generate a high count of 4625 events for the same target account or a small set of accounts, while a password spray will generate a low count per account (e.g., 1-2 failures) across many accounts, making it harder to detect with a simple per-IP threshold. In real-world scenarios, attackers may rotate IPs or use distributed botnets to evade such rules, requiring additional correlation across source IPs or user accounts.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Security and Risk Management — This question tests Security and Risk Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Brute force attack from a single source IP — The SIEM correlation rule counts failed login attempts from a single source IP within a defined time window (e.g., 10 failures in 5 minutes). When the threshold is exceeded, it triggers an alert. This pattern is characteristic of a brute force attack, where an attacker tries many passwords against one account or a few accounts from the same IP address.
What should I do if I get this CISSP question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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