easyMultiple Choice
200-201 Practice Question: A security analyst is reviewing a Snort alert…
A security analyst is reviewing a Snort alert that triggered on the signature 'ET TROJAN Win.Trojan.Generic'. What is the most likely reason this alert fired?
⚠ Common exam trap
Cisco often tests the distinction between signature categories (e.g., Trojan vs. exploit vs. policy violation) to see if candidates understand that each signature type is tailored to a specific threat behavior, not just any anomaly.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A system infected with a trojan
The Snort signature 'ET TROJAN Win.Trojan.Generic' is designed to detect network traffic patterns or payloads associated with known Trojan malware. When this alert fires, it indicates that the sensor observed data matching the signature's characteristics, most likely from a system that is infected with a Trojan and is communicating with a command-and-control server or performing malicious activity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A system infected with a trojan
Why this is correct
The signature name 'ET TROJAN Win.Trojan.Generic' explicitly categorises the traffic as trojan-related, so the alert indicates a host is infected with trojan malware. Snort matches packet patterns against this rule, and the ET prefix confirms it originates from the Emerging Threats ruleset, which targets known malicious trojan behaviour.
- ✗
A legitimate Windows update
Why it's wrong here
A legitimate Windows update would not match a trojan signature, because Snort rules key on known malicious payload patterns, ports and byte sequences rather than on vendor patch traffic. It is tempting as a false-positive explanation, but it would fit only if the signature were a generic protocol or policy rule, not a named trojan.
- ✗
A misconfigured firewall
Why it's wrong here
A misconfigured firewall changes permitted or blocked flows, not the payload content Snort inspects; the signature matched trojan-specific byte patterns in traffic that actually traversed the sensor. It is tempting when ruling out false positives, but it would be correct only for signature alerts caused by rule or placement errors, not content matches.
- ✗
An attacker attempting to exploit a buffer overflow
Why it's wrong here
A buffer overflow exploit targets memory corruption in a vulnerable service; the ET TROJAN signature matches known trojan payload or command-and-control patterns, not exploit-specific overflow byte sequences. It is tempting because exploits are malicious traffic, but it would be correct for an exploit or shellcode signature, not a trojan detection.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.