The answer is port scanning, as the firewall log reveals denied TCP traffic from an internal host to an external IP across consecutive ports, which is the classic signature of reconnaissance activity. This sequential pattern of connection attempts to multiple ports on the same target indicates an attacker probing for open services, specifically a TCP connect scan, where each denied packet represents a failed probe. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to distinguish between normal traffic and malicious reconnaissance by analyzing firewall logs—a core skill for detecting port scanning detection in real-world security operations. A common trap is confusing this with a denial-of-service attack, but remember that port scans target multiple ports on a single host, not a single port across many hosts. Memory tip: think “sequential ports, single target” equals a scan.
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
Exhibit
Refer to the exhibit.
syslog: %ASA-4-106023: Deny tcp src inside:10.0.0.10/12345 dst outside:203.0.113.5/22 by access-group "OUTSIDE" [0x0, 0x0]
syslog: %ASA-4-106023: Deny tcp src inside:10.0.0.10/12346 dst outside:203.0.113.5/23 by access-group "OUTSIDE" [0x0, 0x0]
syslog: %ASA-4-106023: Deny tcp src inside:10.0.0.10/12347 dst outside:203.0.113.5/25 by access-group "OUTSIDE" [0x0, 0x0]
Refer to the exhibit. A firewall log shows denied TCP traffic from an internal host to an external IP on consecutive ports. What type of activity is indicated?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Port scanning
The firewall log shows denied TCP traffic from an internal host to an external IP on consecutive ports. This sequential pattern of connection attempts to multiple ports on the same target is a classic indicator of a port scan, where an attacker probes for open ports to identify potential services to exploit. The firewall's deny action confirms the traffic was blocked, but the behavior itself is characteristic of reconnaissance activity, specifically a TCP connect scan.
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.
✓
Port scanning
Why this is correct
The pattern of denied connections to consecutive ports indicates a scan.
Related concept
Read the scenario before looking for a memorised answer.
✗
Worm propagation
Why it's wrong here
Worm would target multiple hosts, not ports on one host.
✗
Denial of service
Why it's wrong here
DoS would send many packets to a single port.
✗
Data exfiltration
Why it's wrong here
Exfiltration typically uses a single port.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between reconnaissance (port scanning) and exploitation (worm propagation) by presenting a log of denied traffic to consecutive ports, leading candidates to confuse the scanning phase with the actual attack phase, such as worm propagation or DoS.
Detailed technical explanation
How to think about this question
A TCP connect scan completes the full three-way handshake (SYN, SYN-ACK, ACK) on open ports, while closed ports return RST packets; the firewall log here shows denied traffic, meaning the firewall dropped the initial SYN packets before any handshake could occur. In real-world scenarios, attackers often use tools like Nmap with the '-sT' flag for TCP connect scans, and firewalls may log such patterns as 'port scan' events, triggering alerts in intrusion detection systems (IDS) like Snort or Suricata. The consecutive port pattern (e.g., 80, 81, 82) is a giveaway because legitimate traffic rarely accesses multiple sequential ports from a single host in a short time window.
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.
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: Port scanning — The firewall log shows denied TCP traffic from an internal host to an external IP on consecutive ports. This sequential pattern of connection attempts to multiple ports on the same target is a classic indicator of a port scan, where an attacker probes for open ports to identify potential services to exploit. The firewall's deny action confirms the traffic was blocked, but the behavior itself is characteristic of reconnaissance activity, specifically a TCP connect scan.
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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Question Discussion
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