Quick Answer
The answer is UDP packet loss. This is the most likely cause because UDP is a connectionless, best-effort transport protocol that inherently lacks any retransmission or acknowledgment mechanism; when network congestion occurs during peak traffic hours, routers and switches will drop UDP datagrams without notification, and the SIEM simply never receives those events. On the CISSP exam, this scenario tests your understanding of the OSI model’s Transport Layer and the fundamental trade-off between UDP’s speed and its unreliability—a common trap is to blame the SIEM configuration or the log source itself, but the core issue is the protocol’s design. Remember the mnemonic: UDP stands for Unreliable Datagram Protocol, so if events are missing, always suspect the network, not the collector.
This CISSP 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.
An organization uses a siem to collect logs from multiple sources. The security team notices that some events are missing during peak traffic hours. Analysis shows that the log sources are sending data via UDP. What is the most likely cause?
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.
Clock skew between sources and SIEM
Why wrong: Clock skew does not cause loss of events.
Insufficient SIEM storage capacity
Why wrong: Storage would not cause missing events during transmission.
UDP packet loss
UDP does not guarantee delivery; packets can be lost.
Network bandwidth saturation
Why wrong: Bandwidth could cause drops, but UDP is inherently unreliable.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
UDP packet loss
UDP is a connectionless, best-effort transport protocol that does not guarantee delivery. During peak traffic hours, network congestion can cause UDP datagrams to be dropped without any retransmission mechanism, leading to missing events in the SIEM. This is the most direct and likely cause given the scenario.
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.
Clock skew between sources and SIEM
Why it's wrong here
Clock skew does not cause loss of events.
Insufficient SIEM storage capacity
Why it's wrong here
Storage would not cause missing events during transmission.
UDP packet loss
Why this is correct
UDP does not guarantee delivery; packets can be lost.
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.
Network bandwidth saturation
Why it's wrong here
Bandwidth could cause drops, but UDP is inherently unreliable.
Common exam traps
The trap here is that candidates may incorrectly attribute missing events to storage or bandwidth issues, but the question specifically highlights UDP as the transport, which directly implies packet loss due to the protocol's lack of reliability.
Detailed technical explanation
UDP (User Datagram Protocol, RFC 768) has no built-in flow control, error recovery, or congestion avoidance. When a router or switch buffer overflows during high traffic, UDP packets are silently dropped. In contrast, TCP would use window scaling and retransmission to recover. SIEM ingestion pipelines often rely on UDP for syslog (port 514) due to low overhead, but this makes them vulnerable to loss under load. A real-world mitigation is to use TCP-based syslog (port 6514) or implement reliable logging protocols like RELP.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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: UDP packet loss — UDP is a connectionless, best-effort transport protocol that does not guarantee delivery. During peak traffic hours, network congestion can cause UDP datagrams to be dropped without any retransmission mechanism, leading to missing events in the SIEM. This is the most direct and likely cause given the scenario.
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 24, 2026
This CISSP 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 CISSP exam.
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