The answer is a brute force attempt on the Telnet service. This is correct because the firewall logs show repeated denied attempts from host 10.0.0.2 to 10.0.0.1 on port 23, which is the default port for Telnet. A brute force attack is characterized by numerous failed connection attempts in a short period, as the attacker systematically tries different username and password combinations to gain unauthorized access. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to identify attack types from firewall logs, a key skill for security monitoring. A common trap is confusing this with a port scan, but a port scan typically targets multiple ports on a single host, whereas this log shows repeated attempts to the same port (23) on the same destination. Remember the mnemonic “23 for Telnet, many fails means brute force.”
200-201 Host-Based Analysis Practice Question
This 200-201 practice question tests your understanding of host-based analysis. 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.
Mar 1 10:15:22 host1 syslog: [CISCO] %SEC-6-IPACCESSLOGP: list inbound denied tcp 10.0.0.2(49152) -> 10.0.0.1(23), 1 packet
Mar 1 10:15:23 host1 syslog: [CISCO] %SEC-6-IPACCESSLOGP: list inbound denied tcp 10.0.0.2(49153) -> 10.0.0.1(23), 1 packet
Mar 1 10:15:24 host1 syslog: [CISCO] %SEC-6-IPACCESSLOGP: list inbound denied tcp 10.0.0.2(49154) -> 10.0.0.1(23), 1 packet
Refer to the exhibit. A network analyst sees repeated denied attempts from host 10.0.0.2 to 10.0.0.1 on port 23. Based on the log, what type of activity is most likely occurring?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Brute force attempt on Telnet service
The log shows repeated denied attempts from host 10.0.0.2 to 10.0.0.1 on port 23, which is the default port for Telnet. Multiple failed connection attempts to a Telnet service indicate a brute force attack, where an attacker tries to guess credentials by repeatedly attempting to log in.
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.
✗
DNS amplification attack
Why it's wrong here
DNS amplification uses UDP port 53, not TCP port 23.
✗
ARP spoofing
Why it's wrong here
ARP spoofing involves ARP packets, not TCP log entries.
✓
Brute force attempt on Telnet service
Why this is correct
Multiple connection attempts to port 23 (Telnet) from the same source indicate a brute force or scanning activity.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
ICMP flood attack
Why it's wrong here
ICMP flood would generate ICMP packets, not TCP connections to port 23.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the association of default port numbers with services (port 23 = Telnet) and expects candidates to recognize that repeated connection attempts to a login service indicate a brute force attack, not a flood or spoofing attack.
Detailed technical explanation
How to think about this question
Telnet (port 23) transmits data in cleartext, making it a prime target for brute force attacks where an attacker systematically tries username/password combinations. Repeated denied attempts in logs often trigger rate-limiting or account lockout policies, but without such protections, the attacker can eventually gain access. In real-world scenarios, brute force attacks on Telnet are common against legacy devices like routers or switches that still have Telnet enabled.
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 practitioner preparing for the 200-201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
Host-Based Analysis — This question tests Host-Based Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Brute force attempt on Telnet service — The log shows repeated denied attempts from host 10.0.0.2 to 10.0.0.1 on port 23, which is the default port for Telnet. Multiple failed connection attempts to a Telnet service indicate a brute force attack, where an attacker tries to guess credentials by repeatedly attempting to log in.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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