Quick Answer
The answer is DNS tunneling, which is the most likely technique being used for data exfiltration in this scenario. DNS tunneling works by encoding stolen data within the fields of DNS queries and responses, allowing attackers to bypass network security controls because UDP port 53 is almost always permitted through firewalls. The regular intervals of large data transfers to an external IP address are a hallmark of this method, as the attacker fragments the exfiltrated data into many small DNS queries to avoid raising immediate alarms. On the ISC2 Certified in Cybersecurity CC exam, this question tests your understanding of how attackers abuse trusted protocols for covert channels; a common trap is confusing DNS tunneling with HTTP or HTTPS exfiltration, but remember that DNS is often less monitored. A helpful memory tip is to think of DNS tunneling as “hiding data in plain sight” by using the phonebook of the internet to smuggle secrets out, one tiny lookup at a time.
This CC 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.
A security analyst investigates a possible data exfiltration. The analyst sees a large amount of data being sent to an external IP address at regular intervals. Which of the following is the most likely technique being used?
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.
DNS tunneling
DNS tunneling encodes data in DNS requests, allowing stealthy exfiltration.
SQL injection
Why wrong: SQL injection targets databases but does not necessarily result in regular data dumps to an external IP.
Phishing
Why wrong: Phishing is an initial access method, not data exfiltration.
Man-in-the-middle
Why wrong: MITM intercepts traffic, but does not typically involve regular large data transfers to an external IP.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DNS tunneling
DNS tunneling encodes data within DNS queries and responses, allowing attackers to bypass network security controls by exfiltrating data through UDP port 53, which is often allowed through firewalls. The regular intervals of large data transfers to an external IP address are characteristic of a DNS tunnel, as the attacker segments data into multiple DNS queries to avoid detection.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DNS tunneling
Why this is correct
DNS tunneling encodes data in DNS requests, allowing stealthy exfiltration.
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.
SQL injection
Why it's wrong here
SQL injection targets databases but does not necessarily result in regular data dumps to an external IP.
Phishing
Why it's wrong here
Phishing is an initial access method, not data exfiltration.
Man-in-the-middle
Why it's wrong here
MITM intercepts traffic, but does not typically involve regular large data transfers to an external IP.
Common exam traps
ISC2 often tests DNS tunneling as a data exfiltration technique because candidates may overlook that DNS traffic is commonly allowed through firewalls, making it a stealthy channel compared to other attack methods.
Detailed technical explanation
DNS tunneling works by encapsulating non-DNS data (e.g., files, commands) into the query or response fields of DNS packets, often using base64 encoding or custom encoding schemes. The attacker sets up a malicious DNS server that decodes the tunneled data, and the client sends queries for subdomains like 'exfiltrateddata.evil.com', with each query carrying a small chunk of data. Real-world detection involves monitoring for unusual DNS query sizes, high query volumes per domain, or TXT record responses with non-standard content.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
An employee at a financial services firm receives an email that appears to come from the IT helpdesk, asking them to reset their password via a link. The link leads to a convincing fake portal that harvests credentials. Security teams use phishing simulations and security-awareness training to reduce this attack vector. Questions like this test whether you can identify social engineering techniques and appropriate controls.
What to study next
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FAQ
Security Operations — This question tests Security Operations — Read the scenario before looking for a memorised answer..
The correct answer is: DNS tunneling — DNS tunneling encodes data within DNS queries and responses, allowing attackers to bypass network security controls by exfiltrating data through UDP port 53, which is often allowed through firewalls. The regular intervals of large data transfers to an external IP address are characteristic of a DNS tunnel, as the attacker segments data into multiple DNS queries to avoid detection.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This CC practice question is part of Courseiva's free ISC2 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 CC exam.
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