The answer is that the host is infected with malware performing a SYN flood denial-of-service attack. This is correct because a high volume of outbound TCP SYN packets to multiple external IPs on port 443, with no corresponding SYN-ACK responses, indicates the host is generating spoofed or unreachable SYN requests to exhaust target connection tables—a classic SYN flood behavior. On the Cisco SCOR 350-701 exam, this scenario tests your ability to differentiate between malware-driven DoS activity and normal scanning or misconfiguration; a common trap is confusing this with a port scan, but the lack of any SYN-ACK replies points to a one-way flood, not a handshake attempt. Remember the key clue: no SYN-ACKs means the targets never respond, which is the hallmark of a spoofed-source SYN flood. Memory tip: “SYN out, no ACK back—malware’s on the attack.”
350-701 Security Concepts Practice Question
This 350-701 practice question tests your understanding of security concepts. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 engineer is analyzing logs from a Cisco ASA. They notice that a specific internal host is generating a high volume of outbound TCP SYN packets to multiple external IP addresses on port 443, but no SYN-ACK responses are received. What is the most likely explanation?
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
✓
The host is infected with malware that is performing a SYN flood denial-of-service attack
Option C is correct because the host is sending a high volume of TCP SYN packets to multiple external IPs on port 443 without receiving SYN-ACK responses, which is characteristic of a SYN flood attack. In a SYN flood, the attacker (or infected host) sends many SYN packets to exhaust the target's connection table, but the lack of SYN-ACK responses indicates the targets are not completing the handshake, often because the source IP is spoofed or the targets are unresponsive. The Cisco ASA logs show outbound SYN packets with no corresponding SYN-ACKs, which aligns with the host being used as a source for a denial-of-service attack.
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.
✗
The ASA is configured to block outbound HTTPS traffic
Why it's wrong here
If HTTPS were blocked, the ASA would drop the SYN packets, not allow them out.
✗
The host is downloading a large malware file via HTTPS
Why it's wrong here
Downloading a file would require a completed TCP handshake and data transfer.
✓
The host is infected with malware that is performing a SYN flood denial-of-service attack
Why this is correct
Spoofed or high-volume SYN packets without responses indicate a SYN flood attack.
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.
✗
The host is establishing legitimate HTTPS connections
Why it's wrong here
Legitimate HTTPS connections would show SYN-ACK responses.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a host being the source of an attack versus being the victim, and the trap here is that candidates may assume the host is simply making legitimate outbound connections (Option D) without recognizing that the absence of SYN-ACK responses is the key anomaly that indicates an attack rather than normal traffic.
Trap categories for this question
Command / output trap
Legitimate HTTPS connections would show SYN-ACK responses.
Detailed technical explanation
How to think about this question
A SYN flood exploits the TCP three-way handshake by sending a barrage of SYN packets with spoofed source IPs, causing the target to allocate resources for half-open connections until its backlog queue overflows. The Cisco ASA can mitigate this with TCP intercept or SYN flood protection features, but in this case, the host itself is the attacker, not the target. In real-world scenarios, such behavior often indicates a botnet member or a compromised device used in a DDoS campaign, and the ASA logs can be correlated with NetFlow or SNMP data to identify the infected host.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Concepts — This question tests Security Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The host is infected with malware that is performing a SYN flood denial-of-service attack — Option C is correct because the host is sending a high volume of TCP SYN packets to multiple external IPs on port 443 without receiving SYN-ACK responses, which is characteristic of a SYN flood attack. In a SYN flood, the attacker (or infected host) sends many SYN packets to exhaust the target's connection table, but the lack of SYN-ACK responses indicates the targets are not completing the handshake, often because the source IP is spoofed or the targets are unresponsive. The Cisco ASA logs show outbound SYN packets with no corresponding SYN-ACKs, which aligns with the host being used as a source for a denial-of-service attack.
What should I do if I get this 350-701 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: "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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