The answer is unusual outbound traffic to a foreign IP and unexpected large file transfers via FTP. These are the two most likely indicators of data exfiltration because FTP is a clear-text protocol that attackers commonly abuse to compress and upload stolen data in bulk, while a sudden spike in outbound traffic to an unfamiliar external address directly signals that data is leaving the network. On the ISC2 Certified in Cybersecurity CC exam, this concept tests your understanding of the Cyber Kill Chain’s exfiltration phase and your ability to distinguish normal network behavior from malicious activity. A common trap is focusing on inbound threats or encrypted traffic, but remember that exfiltration is about data leaving, not entering. For a quick memory tip, think “FTP Out = Files Taken Out” to recall that large FTP transfers to unknown IPs are a primary red flag.
ISC2 CC Security Operations Practice Question
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 operations center (SOC) analyst is investigating a potential data exfiltration. Which two indicators are most likely signs of data exfiltration?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Unexpected large file transfers via FTP
Unexpected large file transfers via FTP are a classic indicator of data exfiltration because FTP is a clear-text protocol often used to move bulk data out of a network. A sudden spike in outbound FTP traffic, especially to an unfamiliar external IP, suggests an attacker is compressing and uploading stolen files. This behavior directly matches the exfiltration phase of the Cyber Kill Chain.
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.
✗
Large number of failed login attempts
Why it's wrong here
Failed logins indicate brute force, not exfiltration.
✗
Frequent DNS queries to known malicious domains
Why it's wrong here
DNS queries may indicate C2 communication, not direct exfiltration.
✓
Unexpected large file transfers via FTP
Why this is correct
Large file transfers out of the network are a classic exfiltration sign.
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.
✗
Multiple antivirus alerts
Why it's wrong here
Antivirus alerts indicate malware, not necessarily exfiltration.
✓
Unusual outbound traffic to a foreign IP
Why this is correct
Outbound traffic to unfamiliar IPs could indicate data being sent out.
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
ISC2 often tests the distinction between indicators of compromise (IOCs) for different attack phases—candidates confuse C2 beaconing (DNS queries) with data exfiltration (large file transfers), or mistake authentication failures for exfiltration activity.
Detailed technical explanation
How to think about this question
FTP uses TCP port 21 for control and port 20 for data transfer, and large outbound transfers can be detected via netflow or firewall logs showing high byte counts to a single external IP. In real-world scenarios, attackers often rename exfiltrated files with benign extensions (e.g., .txt or .zip) to evade DLP filters, making volume-based anomaly detection critical. RFC 959 defines FTP's data transfer modes, and passive mode (PASV) is commonly used to bypass restrictive firewalls.
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 security analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
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: Unexpected large file transfers via FTP — Unexpected large file transfers via FTP are a classic indicator of data exfiltration because FTP is a clear-text protocol often used to move bulk data out of a network. A sudden spike in outbound FTP traffic, especially to an unfamiliar external IP, suggests an attacker is compressing and uploading stolen files. This behavior directly matches the exfiltration phase of the Cyber Kill Chain.
What should I do if I get this CC 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.
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