200-201 Security Monitoring Practice Question
A security analyst is reviewing NetFlow records exported from a Cisco router at the internet edge. During a suspected ransomware staging window, a single internal host shows a sustained outbound flow to one external IP on TCP 443 with 4.2 GB transferred over 40 minutes, while the host's normal baseline for that destination is under 5 MB per day. No corresponding proxy log entry exists for this session. Which conclusion is best supported by these records?
⚠ Common exam trap
The trap here is assuming that traffic on TCP 443 is inherently safe because it is HTTPS, when the port number says nothing about whether the transfer is authorized or inspected.
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
✓
The records indicate probable data exfiltration or bulk upload over TLS, because the volume and duration are anomalous for that host and bypass the monitored proxy.
NetFlow provides metadata such as byte counts, duration, ports, and endpoints without payload. When one host suddenly sends gigabytes to a single external address far above its baseline and no proxy record exists, the strongest supported hypothesis is bulk outbound transfer, consistent with exfiltration or staged upload. The absence of proxy inspection suggests the session avoided the monitored path, reinforcing the need to escalate and correlate with endpoint and DNS telemetry.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The flow confirms a denial-of-service attack because large outbound transfers consume bandwidth and degrade availability.
Why it's wrong here
Denial-of-service is characterized by flooding a target to exhaust its resources, typically inbound to the victim service. Here one internal host is sending data outbound to one external peer, which is a transfer pattern, not a flood. Bandwidth consumption alone does not make this a DoS event, and no availability impact on a target is described.
- ✗
The flow is normal because TCP 443 is reserved for HTTPS and traffic on that port is always legitimate business use.
Why it's wrong here
Port 443 is a service port convention, not a trust guarantee. Attackers routinely tunnel C2, ransomware staging, and exfiltration over TLS on 443 precisely because it blends with web traffic. Treating every 443 session as benign ignores the anomalous volume, the off-baseline destination, and the absence of a proxy record, all of which contradict this reasoning.
- ✗
The flow represents encrypted command-and-control beaconing because beaconing is identified by high byte volume on port 443.
Why it's wrong here
Beaconing is characterized by small, regularly spaced check-ins, not 4.2 GB in 40 minutes. This flow volume is far outside the pattern analysts attribute to periodic C2 polling. The absence of a proxy log also points to a non-proxied transfer rather than a beacon, so this option misreads the traffic profile entirely for the described scenario.
- ✓
The records indicate probable data exfiltration or bulk upload over TLS, because the volume and duration are anomalous for that host and bypass the monitored proxy.
Why this is correct
A single host pushing 4.2 GB to one external address in 40 minutes, hundreds of times above its own baseline, matches bulk outbound transfer behavior. The missing proxy log means the session did not traverse the inspected path, so content was likely TLS-encrypted and uninspected. NetFlow alone cannot prove exfiltration, but it strongly supports this hypothesis and warrants escalation.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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