GPEN Reconnaissance Practice Question
You are conducting an external penetration test against a client who uses a split-horizon DNS configuration. You want to identify internal hostnames and IP addresses without sending any traffic to the client's internal network. Which of the following techniques would best accomplish this?
⚠ Common exam trap
The trap here is assuming that any DNS query against the target's infrastructure is passive, when in fact only third-party data sources like passive DNS and CT logs avoid touching the target.
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
✓
Analyze historical DNS data from passive DNS databases and certificate transparency logs
Split-horizon DNS separates internal and external views, so external queries won't reveal internal names. Passive DNS and certificate transparency logs are public data sources that may contain leaked internal hostnames from misconfigured certificates or historical records. These sources require no interaction with the target's infrastructure, making them ideal for stealthy reconnaissance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Perform DNS cache snooping against the internal recursive resolver
Why it's wrong here
Cache snooping requires sending queries to the internal recursive resolver, which is an active technique that sends traffic to the internal network. It also only reveals recently cached records, not the full internal namespace. This would not meet the requirement of avoiding traffic to the internal network and is unlikely to yield comprehensive internal hostnames.
- ✗
Use DNS zone transfer requests against the external authoritative name servers
Why it's wrong here
Zone transfers against external authoritative servers typically only reveal public DNS records, not internal hostnames. In a split-horizon setup, the external view is intentionally limited. Even if a zone transfer succeeds, it would not expose the internal namespace, which is served by separate internal DNS servers that are not accessible externally.
- ✓
Analyze historical DNS data from passive DNS databases and certificate transparency logs
Why this is correct
Passive DNS databases and certificate transparency logs aggregate historical DNS resolutions and SSL/TLS certificate issuances without sending any traffic to the target. They can reveal internal hostnames that were previously exposed in public certificates or DNS queries. This is a purely passive technique that aligns with the requirement to avoid internal network traffic.
- ✗
Query the internal DNS server directly using its private IP address
Why it's wrong here
Directly querying the internal DNS server requires network access to the private IP address, which you do not have from an external perspective. This would be an active technique that sends traffic to the internal network, violating the requirement to avoid touching the internal network. It also assumes the internal DNS server is reachable, which is unlikely from the internet.
Visual reference
About these practice questions
This GPEN question is part of Courseiva's 298-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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 GIAC exam blueprint
This GPEN practice question is part of Courseiva's free GIAC 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 GPEN exam.