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CAS-004 Practice Question: A security analyst is reviewing alerts from a…
A security analyst is reviewing alerts from a SIEM and notices multiple failed login attempts from a single IP address to different user accounts over a 5-minute window. What should the analyst do FIRST?
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
✓
Check the source IP and correlate with other logs to confirm suspicious activity.
In incident response, the first step is to verify the alert before taking any action. The analyst should check the source IP and correlate the failed login attempts with other logs (e.g., VPN logs, IDS alerts, or previous successful logins) to determine if this is a brute-force attack, a misconfigured application, or a false positive. Prematurely blocking the IP (option A) could disrupt legitimate traffic if the IP is a shared proxy or NAT. Isolating endpoints (option B) is excessive without confirmation that the attempts were successful or that the endpoints are compromised. Resetting all targeted accounts (option D) is disruptive and unnecessary without evidence of compromise. Therefore, the correct first step is to verify and correlate the alert (option C).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Block the IP address at the firewall.
Why it's wrong here
Blocking without verification could be a false positive and may impact legitimate users.
- ✗
Isolate all endpoints that received the login attempts.
Why it's wrong here
Isolating endpoints is a drastic measure and should only be done if compromise is confirmed.
- ✓
Check the source IP and correlate with other logs to confirm suspicious activity.
Why this is correct
Verification is the first step before taking action.
- ✗
Reset all user accounts that were targeted.
Why it's wrong here
Resetting accounts is disruptive and may not be necessary if the attempts are automated bots.
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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.