The answer is a sudden spike in DNS queries to unknown domains from a single host and multiple outbound connections from a server to an external IP on port 445. These are classic indicators of network intrusion because DNS tunneling exploits the allowed DNS protocol to exfiltrate data or establish command-and-control (C2) communication, while unusual outbound SMB traffic on port 445 often signals a compromised server attempting to spread malware or connect to an external attacker. On the Cisco CyberOps Associate 200-201 exam, this question tests your ability to distinguish between benign network behavior and malicious indicators, with a common trap being to overlook that outbound SMB is abnormal for a server. A helpful memory tip is to think of DNS as a "covert channel" and port 445 as the "spread port"—both should raise immediate suspicion when seen in unexpected outbound patterns.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion 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.
Which TWO of the following are indicators of a network intrusion? (Choose two.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A sudden increase in DNS queries to unknown domains from a single host
Option D is correct because a sudden spike in DNS queries to unknown domains from a single host is a classic sign of DNS tunneling or command-and-control (C2) activity. Attackers often use DNS to exfiltrate data or communicate with external servers by encoding data in DNS queries, bypassing traditional firewall rules that allow DNS traffic.
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.
✗
High bandwidth usage during business hours
Why it's wrong here
High bandwidth can be legitimate, e.g., video streaming or backups.
✗
A single failed login attempt from an internal user
Why it's wrong here
One failed login is normal; it does not indicate an intrusion.
✗
Regular ICMP echo requests to external hosts
Why it's wrong here
ICMP echo requests are common for network troubleshooting.
✓
A sudden increase in DNS queries to unknown domains from a single host
Why this is correct
This could indicate malware beaconing or DNS tunneling.
Related concept
Read the scenario before looking for a memorised answer.
✓
Multiple outbound connections from a server to an external IP on port 445
Why this is correct
Port 445 is SMB; outbound SMB from a server may indicate data exfiltration.
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 distinction between normal administrative traffic (like ICMP pings or a single failed login) and true indicators of compromise (like anomalous DNS queries or outbound SMB connections), trapping candidates who mistake benign activity for malicious.
Detailed technical explanation
How to think about this question
DNS tunneling exploits the fact that DNS queries are often allowed through firewalls and inspected only for domain names, not payload content. Tools like dnscat2 or Iodine encode data in subdomains or TXT records, and the sudden increase in unique, random-looking domain queries from a single host is a strong indicator. Similarly, outbound connections on port 445 (SMB) from a server to an external IP are highly suspicious because SMB is typically used for internal file sharing and should not be initiated to external addresses; this often indicates lateral movement or data exfiltration via SMB over the internet.
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.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A sudden increase in DNS queries to unknown domains from a single host — Option D is correct because a sudden spike in DNS queries to unknown domains from a single host is a classic sign of DNS tunneling or command-and-control (C2) activity. Attackers often use DNS to exfiltrate data or communicate with external servers by encoding data in DNS queries, bypassing traditional firewall rules that allow DNS traffic.
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.
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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