The best immediate action for repeated failed logins from a single IP is to block that source IP address on the firewall. This stops the ongoing brute-force attack at the network perimeter by preventing any further authentication attempts from that address, which aligns with the containment-before-investigation principle in incident response. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your understanding of the first step in the NIST incident response framework—containment—and distinguishes it from actions like disabling user accounts or analyzing logs, which are secondary steps. A common trap is to focus on the targeted accounts rather than the attacking IP, but remember that blocking the IP preserves evidence and halts the attack without disrupting legitimate users. Memory tip: “IP first, accounts later—firewall is the gatekeeper.”
200-201 Security Monitoring Practice Question
This 200-201 practice question tests your understanding of security monitoring. 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.
A security analyst notices repeated failed login attempts from a single IP address against multiple user accounts. What is the best immediate action to take?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Block the source IP address on the firewall.
Blocking the source IP address on the firewall is the best immediate action because it stops the ongoing brute-force attack at the network perimeter, preventing further authentication attempts from that IP without disrupting legitimate users. This aligns with the principle of containment before investigation, as the firewall ACL can be updated quickly to deny traffic from the offending source.
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.
✗
Increase logging verbosity for the authentication server.
Why it's wrong here
Increased logging helps forensics but does not stop the attack.
✗
Change all user passwords immediately.
Why it's wrong here
Changing all passwords is reactive and may not stop the ongoing attack.
✗
Disable the affected user accounts.
Why it's wrong here
Disabling accounts disrupts users and may not be necessary if the attack is mitigated.
✓
Block the source IP address on the firewall.
Why this is correct
Blocking the IP address stops the brute-force attempt immediately.
Clue confirmation
The clue word "best" 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
Cisco often tests the candidate's ability to prioritize containment over investigation or remediation; the trap here is that candidates may choose to increase logging (Option A) to gather evidence, but the immediate action must stop the active attack first.
Detailed technical explanation
How to think about this question
In a brute-force attack, the attacker typically uses automated scripts to send repeated authentication requests (e.g., over SSH, RDP, or HTTP Basic Auth). Blocking the source IP at the firewall using an ACL or a dynamic block rule (e.g., via a next-generation firewall or IPS) immediately terminates the TCP/UDP sessions from that host, effectively stopping the attack at Layer 3/4. This approach is preferred over rate-limiting at the application layer because it offloads the blocking to the network device and does not consume authentication server resources.
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 administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Monitoring — This question tests Security Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Block the source IP address on the firewall. — Blocking the source IP address on the firewall is the best immediate action because it stops the ongoing brute-force attack at the network perimeter, preventing further authentication attempts from that IP without disrupting legitimate users. This aligns with the principle of containment before investigation, as the firewall ACL can be updated quickly to deny traffic from the offending source.
What should I do if I get this 200-201 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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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