- A
A single large file upload to a cloud service
Why wrong: A single upload suggests data exfiltration but does not indicate a persistent backdoor; it may be a one-time event.
- B
Regular beaconing to an external IP on a high port
Regular beaconing is a hallmark of persistent C2 communication, indicating a backdoor that periodically checks in.
- C
A change in the host's registry
Why wrong: A registry change is a host-based indicator, not visible in a network pcap, and is not a direct network evidence.
- D
An SSH connection from an external IP
Why wrong: An SSH connection could be legitimate remote access and does not by itself indicate a persistent backdoor.
- E
DNS queries with subdomains that encode data
DNS tunneling using encoded subdomains is a technique for persistent covert communication and data exfiltration.
Quick Answer
The answer is DNS queries with subdomains that encode data and regular beaconing to an external IP on a high port. These two pieces of evidence directly indicate a persistent backdoor because the compromised host uses DNS tunneling to exfiltrate data or receive commands by encoding payloads within subdomain labels, while periodic beaconing establishes a reliable command-and-control (C2) channel on a non-standard high port to evade basic firewall filters. On the Cisco CyberOps Associate 200-201 exam, this question tests your ability to distinguish persistent backdoor indicators from one-time exploit artifacts in a pcap file; a common trap is mistaking a single large data transfer for persistence, when in fact regular, low-and-slow beaconing or encoded DNS queries reveal an ongoing foothold. Remember the mnemonic “DNS + Beacon = Backdoor” to link these two telltale signs of a lasting compromise.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
An analyst is investigating a host that was compromised via a web exploit. The analyst has a pcap file of the network traffic. Which TWO pieces of evidence would indicate that the attacker established a persistent backdoor?
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
Regular beaconing to an external IP on a high port
Regular beaconing to an external IP on a high port (Option B) is a classic indicator of a persistent backdoor because the compromised host periodically initiates outbound connections to a command-and-control (C2) server, often using non-standard high ports (e.g., 4444, 8080, or 1337) to evade firewall rules. This behavior maintains a communication channel that allows the attacker to issue commands or exfiltrate data over time, even if the initial exploit vector is patched.
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.
- ✗
A single large file upload to a cloud service
Why it's wrong here
A single upload suggests data exfiltration but does not indicate a persistent backdoor; it may be a one-time event.
- ✓
Regular beaconing to an external IP on a high port
Why this is correct
Regular beaconing is a hallmark of persistent C2 communication, indicating a backdoor that periodically checks in.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A change in the host's registry
Why it's wrong here
A registry change is a host-based indicator, not visible in a network pcap, and is not a direct network evidence.
- ✗
An SSH connection from an external IP
Why it's wrong here
An SSH connection could be legitimate remote access and does not by itself indicate a persistent backdoor.
- ✓
DNS queries with subdomains that encode data
Why this is correct
DNS tunneling using encoded subdomains is a technique for persistent covert communication and 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 network-based evidence (pcap) and host-based evidence (registry changes), so candidates may incorrectly select Option C because they confuse persistence mechanisms with the type of data available in a packet capture.
Detailed technical explanation
How to think about this question
DNS queries with subdomains that encode data (Option E) are a form of DNS tunneling, where the attacker embeds exfiltrated data or C2 commands within DNS query subdomains (e.g., base64-encoded payloads in 'aGVsbG8uZXZpbC5jb20'). This technique exploits the fact that DNS traffic is often allowed through firewalls, and the responses can carry commands back to the host, enabling a stealthy persistent backdoor that blends with legitimate DNS traffic.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-201 question test?
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: Regular beaconing to an external IP on a high port — Regular beaconing to an external IP on a high port (Option B) is a classic indicator of a persistent backdoor because the compromised host periodically initiates outbound connections to a command-and-control (C2) server, often using non-standard high ports (e.g., 4444, 8080, or 1337) to evade firewall rules. This behavior maintains a communication channel that allows the attacker to issue commands or exfiltrate data over time, even if the initial exploit vector is patched.
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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Last reviewed: Jun 25, 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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