- A
DNS tunneling
Why wrong: DNS uses port 53, not 25.
- B
Secure web browsing
Why wrong: Web browsing uses ports 80/443.
- C
Data exfiltration using FTP
Why wrong: FTP uses ports 20/21, not 25.
- D
Spam email campaign or SMTP scanning
SMTP port 25 is used for email; many connections to various external IPs could indicate scanning for open relays or sending spam.
Question 868 of 1,000
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 Zeek connection log shows a high number of connections from a single internal IP to many different external IPs on port 25, with small payload sizes. Which behavior is most likely indicated?
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 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
✓
Spam email campaign or SMTP scanning
Port 25 is the default SMTP port used for email transmission. A high volume of connections from a single internal IP to many different external IPs on port 25, with small payload sizes, is characteristic of a spam email campaign or SMTP scanning. This pattern suggests the host is either sending bulk spam emails or probing external mail servers for open relay or user enumeration.
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 tunneling
Why it's wrong here
DNS uses port 53, not 25.
- ✗
Secure web browsing
Why it's wrong here
Web browsing uses ports 80/443.
- ✗
Data exfiltration using FTP
Why it's wrong here
FTP uses ports 20/21, not 25.
- ✓
Spam email campaign or SMTP scanning
Why this is correct
SMTP port 25 is used for email; many connections to various external IPs could indicate scanning for open relays or sending spam.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the association of well-known ports with their protocols, and the trap here is that candidates may confuse port 25 with other common ports like 53 (DNS) or 21 (FTP), leading them to select DNS tunneling or FTP exfiltration instead of recognizing the SMTP spam pattern.
Detailed technical explanation
How to think about this question
SMTP (Simple Mail Transfer Protocol) uses port 25 for relaying email between mail servers. In a spam campaign, the sending host often uses a script to connect to multiple external mail servers, sending small email messages (often with minimal content) to test relay capabilities or deliver spam. Zeek's conn.log captures the 5-tuple (src IP, dst IP, src port, dst port, protocol), and a high count of unique dst IPs on port 25 with small payloads is a classic indicator of SMTP scanning or spamming behavior.
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.
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FAQ
Questions learners often ask
What does this 200-201 question test?
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: Spam email campaign or SMTP scanning — Port 25 is the default SMTP port used for email transmission. A high volume of connections from a single internal IP to many different external IPs on port 25, with small payload sizes, is characteristic of a spam email campaign or SMTP scanning. This pattern suggests the host is either sending bulk spam emails or probing external mail servers for open relay or user enumeration.
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.
About these practice questions
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Last reviewed: Jul 4, 2026
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.
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