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CAS-004 Practice Question: A financial organization's SOC analysts have…
A financial organization's SOC analysts have observed repeated failed authentication attempts from a single external IP address against multiple user accounts, followed by a successful authentication from the same IP using one of those accounts. Which type of security monitoring rule would be most effective at detecting this attack pattern in real 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
✓
Alert when multiple failed logins from a single source IP are followed by a successful login from that IP within 10 minutes.
The observed attack pattern is a credential stuffing attempt: multiple failed logins from a single external IP followed by a successful login from that same IP. Option A directly detects this by correlating multiple failures and a subsequent success from the same source IP within a short time window. This is the most effective real-time detection rule for such behavior. Option B targets a single user account, not the source IP, so it would miss the pattern if the attacker uses different users. Option C is unrelated (password reset success). Option D would generate excessive false positives by alerting on any single failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Alert when multiple failed logins from a single source IP are followed by a successful login from that IP within 10 minutes.
Why this is correct
This correlation rule accurately detects the credential stuffing pattern across different accounts from one IP.
- ✗
Alert when a user account has three failed logins within 5 minutes followed by a successful login.
Why it's wrong here
This targets multiple failures on one account, but the attack uses multiple accounts from one IP.
- ✗
Alert when a successful authentication occurs immediately after a password reset.
Why it's wrong here
This indicates a possible account takeover after reset, not the described pattern.
- ✗
Alert on any single failed login attempt from an external IP.
Why it's wrong here
A single failure is too noisy and not indicative of the attack.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CAS-005 practice question is part of Courseiva's free CompTIA 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 CAS-005 exam.