Quick Answer
The correct answer is that the traffic is likely generated by malware. This conclusion stems from a fundamental principle of user-agent analysis: a suspicious user-agent that mismatches the host’s known operating system is a classic malware indicator. In this alert, the User-Agent string references Windows NT 5.1, which corresponds to Windows XP, while the source host consistently runs Windows 10—a clear anomaly that malware often exploits to disguise its traffic as legacy browser activity. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to correlate endpoint context with network telemetry, specifically recognizing that outdated or mismatched user-agent strings in HTTP requests are red flags for evasion techniques. A common trap is focusing solely on the alert signature name without verifying the host’s baseline behavior; the mismatch itself is the decisive clue. Memory tip: “XP on a Win 10 box? That’s a malware ox.”
This 200-201 practice question tests your understanding of network intrusion analysis. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 analyst sees an alert: 'ET POLICY Outgoing HTTP Request with Suspicious User-Agent (Mozilla/5.0 compatible; MSIE 6.0; Windows NT 5.1)'. The source is an internal host that typically uses Windows 10. What should the analyst suspect?
The traffic is from a web proxy
Why wrong: No evidence of proxy involvement.
The host is running Windows XP
Why wrong: The host is known to run Windows 10.
The host is running a browser update
Why wrong: Browser updates do not use such an old User-Agent.
The traffic is likely generated by malware
Malware often uses old User-Agents to evade detection.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The traffic is likely generated by malware
The User-Agent string 'Mozilla/5.0 compatible; MSIE 6.0; Windows NT 5.1' mimics Internet Explorer 6 on Windows XP (NT 5.1). Since the source host normally runs Windows 10, this outdated and mismatched User-Agent is a strong indicator of malware attempting to disguise its traffic as legacy browser activity to evade detection.
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.
The traffic is from a web proxy
Why it's wrong here
No evidence of proxy involvement.
The host is running Windows XP
Why it's wrong here
The host is known to run Windows 10.
The host is running a browser update
Why it's wrong here
Browser updates do not use such an old User-Agent.
The traffic is likely generated by malware
Why this is correct
Malware often uses old User-Agents to evade detection.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the concept that an anomalous User-Agent string inconsistent with the host's known OS is a red flag for malware, not an indication of the actual OS version.
Detailed technical explanation
Malware often hardcodes User-Agent strings from older browsers to bypass simple allowlists or to mimic low-risk traffic. The string 'MSIE 6.0; Windows NT 5.1' corresponds to Internet Explorer 6 on Windows XP, an OS no longer supported; legitimate Windows 10 systems would send a User-Agent like 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36...'. Security analysts can use Suricata or Snort rules to flag such mismatches as indicators of compromise.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
The correct answer is: The traffic is likely generated by malware — The User-Agent string 'Mozilla/5.0 compatible; MSIE 6.0; Windows NT 5.1' mimics Internet Explorer 6 on Windows XP (NT 5.1). Since the source host normally runs Windows 10, this outdated and mismatched User-Agent is a strong indicator of malware attempting to disguise its traffic as legacy browser activity to evade detection.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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