The answer is a Denial of Service (DoS) attack. The ASA syslog drop rate exceeded alert, such as %ASA-4-733100, triggers when the firewall’s rate-limit threshold for dropped packets is surpassed, typically due to a flood of incomplete connections like SYN floods or half-open sessions that exhaust system resources. On the Cisco CyberOps Associate 200-201 exam, this message tests your ability to correlate threshold-based alerts with attack patterns, distinguishing DoS from mere network congestion or misconfiguration. A common trap is assuming any high drop rate indicates a hardware failure, but the ASA’s specific “drop rate exceeded” syslog is designed to flag abnormal traffic volumes consistent with DoS. Remember the mnemonic “DROP = Denial Rate Overwhelms Protection” to link the alert directly to a DoS scenario.
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.
%ASA-4-733100: [10.10.10.10] drop rate-1 exceeded. Current burst rate is 1050 bursts per second, max configured rate is 1000.
An analyst sees this syslog message on the Cisco ASA. What is the most likely cause of this alert?
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
✓
A DoS attack
The syslog message likely indicates a high rate of connection attempts or incomplete sessions (e.g., %ASA-4-106017: Deny TCP due to SYN flood or %ASA-4-733100: Drop rate exceeded). This is characteristic of a Denial of Service (DoS) attack, where an attacker overwhelms the firewall with traffic to exhaust resources or disrupt service. Option C is correct because the ASA's threshold-based alerting specifically triggers on abnormal traffic volumes that match DoS patterns.
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.
✗
Normal traffic spike
Why it's wrong here
Normal spikes rarely exceed configured drop rate limits, which are set to allow typical traffic patterns.
✗
A routing loop
Why it's wrong here
Routing loops cause packet TTL expiration, not increased burst rates on a single device.
✓
A DoS attack
Why this is correct
The high burst rate exceeding the configured max is consistent with a DoS attack overwhelming the firewall.
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.
✗
A misconfigured firewall
Why it's wrong here
Misconfiguration typically causes policy violations or connectivity issues, not a burst rate drop alert.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a DoS attack and a misconfiguration by embedding syslog messages that reference rate-based thresholds (e.g., 'Drop rate exceeded') rather than explicit ACL deny messages, leading candidates to mistakenly choose 'misconfigured firewall' when the alert is actually a security event.
Detailed technical explanation
How to think about this question
The Cisco ASA uses a 'threat detection' feature that monitors rates of events such as denied packets, incomplete connections, or SYN segments. When the rate exceeds a configured threshold (e.g., 'threat-detection rate tcp-interval 600 burst 4000'), it generates syslog message %ASA-4-733100. Under the hood, the ASA maintains sliding window counters per protocol and can dynamically rate-limit or shun sources, which is why a DoS attack is the most plausible cause. In real-world scenarios, a sudden spike in half-open connections (SYN_RCVD) from a single source IP is a classic indicator of a SYN flood DoS.
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: A DoS attack — The syslog message likely indicates a high rate of connection attempts or incomplete sessions (e.g., %ASA-4-106017: Deny TCP due to SYN flood or %ASA-4-733100: Drop rate exceeded). This is characteristic of a Denial of Service (DoS) attack, where an attacker overwhelms the firewall with traffic to exhaust resources or disrupt service. Option C is correct because the ASA's threshold-based alerting specifically triggers on abnormal traffic volumes that match DoS patterns.
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.
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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Question Discussion
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