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Incident Response: First Action Is to Block Source IP

Exhibit

Refer to the exhibit.
```
! Threat Alert from SIEM
Event: Multiple failed logins from IP 10.0.0.5
Time: 2025-03-15 14:32:00
User: admin
Source IP: 10.0.0.5
Destination: 192.168.1.100 (SSH)
Count: 50 in 5 minutes

! Firewall Log
2025-03-15 14:35:00, ALLOW, TCP, 10.0.0.5:54321, 192.168.1.100:22, 100 bytes
```

Refer to the exhibit. A security analyst observes a SIEM alert and a firewall log. The firewall allowed the traffic. According to the company's security policy, which action should the analyst take first?

Quick Answer

The correct first action is to block the source IP by creating a firewall rule. This is the immediate response because the firewall log confirms the traffic was allowed, while the SIEM alert signals a security event; according to the security policy, the priority is to stop the active threat at the network edge before conducting deeper analysis. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your understanding of the containment phase in incident response—specifically, that blocking the source IP is a swift, reversible action that prevents further malicious traffic without disrupting the entire network. A common trap is to jump to isolating the host or analyzing logs first, but the policy-driven first action is always to cut off the attacker’s access. Remember the mnemonic “Block First, Ask Later” to reinforce that containment precedes investigation in a live incident.

⚠ Common exam trap

Cisco often tests the candidate's ability to prioritize containment over investigation, leading them to mistakenly choose 'investigate the user's recent activity' instead of immediately blocking the malicious source IP.

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

✓

Create a firewall rule to block the source IP.

The firewall log shows the traffic was allowed, and the SIEM alert indicates a security event. According to the security policy, the immediate action is to block the source IP to prevent further potential malicious activity. Creating a firewall rule to block the source IP is a direct and effective response to mitigate the threat.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • ✗

    Check if the firewall blocked the traffic.

    Why it's wrong here

    The firewall log shows ALLOW, so it did not block.

  • ✗

    Investigate the user's recent activity.

    Why it's wrong here

    Containment should come first; investigation can follow.

  • ✗

    Ignore the alert as it is a false positive.

    Why it's wrong here

    50 failed logins in 5 minutes is a clear brute-force attempt.

  • ✓

    Create a firewall rule to block the source IP.

    Why this is correct

    Immediate containment by blocking the IP is appropriate.

About these practice questions

One of 979 original 200-201 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →

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Same concept, more angles

1 more way this is tested on 200-201

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A security analyst receives an alert that an employee's workstation is generating outbound traffic to a known malware command-and-control IP address at 3:00 AM. According to the company's incident response policy, what is the FIRST action the analyst should take?

easy
  • ✓ A.Isolate the workstation from the network by disabling the switch port.
  • B.Reimage the workstation immediately to remove the malware.
  • C.Apply the latest security patches to the workstation.
  • D.Call the employee to ask if they are working late.

Why A: The first action is to isolate the workstation from the network by disabling the switch port. This immediately stops the outbound command-and-control (C2) traffic, preventing data exfiltration and further compromise, while preserving the system state for forensic analysis. According to the incident response policy, containment takes precedence over eradication or recovery to limit damage.

JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.