200-201 Security Monitoring Practice Question
An analyst receives an IDS alert with signature name 'ET TROJAN Win32.Zeus Checkin' and severity 'high'. The alert shows source IP 192.168.1.50 and destination IP 198.51.100.20 on port 443. Which action should the analyst take FIRST?
⚠ Common exam trap
Cisco often tests the principle that containment (isolating the host) takes precedence over blocking external IPs or performing forensic analysis, and that encryption does not invalidate IDS alerts because signatures can detect malicious patterns in metadata or handshake characteristics.
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
✓
Isolate the source host from the network to prevent further communication.
The alert indicates a high-severity Zeus Trojan check-in, which is a known malware communicating with a command-and-control (C2) server. The first priority is to contain the threat by isolating the source host (192.168.1.50) to prevent further data exfiltration or lateral movement. Even though the traffic is encrypted over port 443 (HTTPS), the signature confirms malicious activity, so immediate isolation is the correct initial response per incident response best practices.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Isolate the source host from the network to prevent further communication.
Why this is correct
The signature indicates an active Zeus trojan check-in from internal host 192.168.1.50 to external infrastructure over port 443, confirming likely compromise and command-and-control beaconing. Isolating that host immediately halts exfiltration and lateral movement, the priority containment step before deeper forensic analysis.
- ✗
Check the host's web browsing history for suspicious websites.
Why it's wrong here
Browsing history is endpoint evidence that may corroborate an infection, but it does not confirm the C2 check-in or contain the threat. It is tempting because Zeus often spreads via malicious sites. The first action should instead validate and scope the alert, for example by checking the destination IP's reputation.
- ✗
Immediately block the destination IP on the firewall.
Why it's wrong here
Blocking the destination IP presumes the alert is a true positive, yet the source 192.168.1.50 is internal and the traffic is outbound TLS on 443, so the analyst must first validate the alert and identify the internal host before any containment. Firewall blocks suit confirmed malicious external command-and-control endpoints.
- ✗
Ignore the alert because the traffic is encrypted over port 443.
Why it's wrong here
TLS encryption hides payload contents, but the IDS signature already matched on metadata such as JA3 fingerprint, certificate or SNI, so the alert carries real signal. Ignoring it discards that detection. Encryption is a reason to pivot to endpoint and proxy telemetry, not to dismiss the alert.
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JA
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.