- A
This is normal DNS behavior, so no action is needed unless users report an outage.
Why wrong: The repeated, structured pattern and random-looking subdomains are not typical of normal business DNS activity. Ignoring it could allow continued compromise.
- B
Suspect DNS-based command-and-control, then isolate the server and collect logs and packet data for analysis.
Regular outbound DNS queries to random subdomains can indicate tunneling or command-and-control traffic. The fact that it repeats at a fixed interval strengthens that suspicion. The best next step is to contain the host so the activity cannot continue, while preserving logs and packet captures for investigation. This lets the team determine whether malware, a rogue process, or a misconfiguration is responsible without losing evidence.
- C
Rotate the DNS server’s administrator password and leave the web server online.
Why wrong: Changing a DNS admin password does not address suspicious outbound traffic from the web server itself. The issue is likely on the endpoint or network path.
- D
Assume the web server is performing routine certificate renewal checks and ignore the alert.
Why wrong: Certificate renewal traffic does not usually produce random-looking subdomains at a fixed interval to an unknown domain. That explanation does not fit the pattern well.
Quick Answer
The best interpretation is that this is DNS tunneling for command and control, and the next step is to isolate the server and collect logs and packet data for analysis. This is correct because small, periodic DNS queries to random-looking subdomains under an unused domain are a classic signature of DNS-based C2 communication, where attackers encode stolen data or commands within DNS requests to bypass firewalls that normally allow DNS traffic. On the Security+ SY0-701 exam, this scenario tests your ability to recognize covert exfiltration channels in network detection and response (NDR) data, often as a distractor against false positives like misconfigured DNS or legitimate service heartbeats. A common trap is assuming the traffic is benign because it uses DNS, but the persistence during idle periods confirms malicious intent. Memory tip: think “DNS Drip” – small, steady queries to odd domains always mean “C2, not a glitch.”
SY0-701 Security Operations Practice Question
This SY0-701 practice question tests your understanding of security operations. 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.
An NDR tool shows a production web server sending small, periodic DNS queries to random-looking subdomains under a domain the company does not use. The pattern repeats every 60 seconds, even when normal web traffic is idle. What is the best interpretation and next step?
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 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
Suspect DNS-based command-and-control, then isolate the server and collect logs and packet data for analysis.
The small, periodic DNS queries to random-looking subdomains under an unused domain are a classic indicator of DNS-based command-and-control (C2) communication. Attackers often use DNS tunneling to exfiltrate data or send commands, as DNS traffic is typically allowed through firewalls. The fact that the pattern persists even during idle web traffic confirms it is not related to normal server operations, making isolation and forensic collection the appropriate next step.
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.
- ✗
This is normal DNS behavior, so no action is needed unless users report an outage.
Why it's wrong here
The repeated, structured pattern and random-looking subdomains are not typical of normal business DNS activity. Ignoring it could allow continued compromise.
- ✓
Suspect DNS-based command-and-control, then isolate the server and collect logs and packet data for analysis.
Why this is correct
Regular outbound DNS queries to random subdomains can indicate tunneling or command-and-control traffic. The fact that it repeats at a fixed interval strengthens that suspicion. The best next step is to contain the host so the activity cannot continue, while preserving logs and packet captures for investigation. This lets the team determine whether malware, a rogue process, or a misconfiguration is responsible without losing evidence.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Rotate the DNS server’s administrator password and leave the web server online.
Why it's wrong here
Changing a DNS admin password does not address suspicious outbound traffic from the web server itself. The issue is likely on the endpoint or network path.
- ✗
Assume the web server is performing routine certificate renewal checks and ignore the alert.
Why it's wrong here
Certificate renewal traffic does not usually produce random-looking subdomains at a fixed interval to an unknown domain. That explanation does not fit the pattern well.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may mistake periodic DNS queries for legitimate maintenance traffic (like certificate renewal or NTP sync) and overlook the key indicator of random-looking subdomains under an unused domain, which is a hallmark of DNS tunneling for C2.
Detailed technical explanation
How to think about this question
DNS tunneling encodes data in DNS query and response packets, often using base32 or base64 encoding in subdomain labels to bypass network controls. Tools like dnscat2 or Iodine can establish a bidirectional C2 channel over UDP port 53, with a beacon interval as short as 60 seconds to maintain stealth. In a real-world incident, analyzing the DNS query payloads with tools like Wireshark or tcpdump can reveal encoded commands or exfiltrated data, and the server's process list should be checked for suspicious processes like 'dnscat' or 'iodine'.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach 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 SY0-701 question test?
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Suspect DNS-based command-and-control, then isolate the server and collect logs and packet data for analysis. — The small, periodic DNS queries to random-looking subdomains under an unused domain are a classic indicator of DNS-based command-and-control (C2) communication. Attackers often use DNS tunneling to exfiltrate data or send commands, as DNS traffic is typically allowed through firewalls. The fact that the pattern persists even during idle web traffic confirms it is not related to normal server operations, making isolation and forensic collection the appropriate next step.
What should I do if I get this SY0-701 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.
About these practice questions
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Last reviewed: Jun 11, 2026
This SY0-701 practice question is part of Courseiva's free CompTIA 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 SY0-701 exam.
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