200-201 Host-Based Analysis Practice Question
When performing file analysis, which method is most reliable for determining the actual file type regardless of its extension?
⚠ Common exam trap
Cisco often tests the concept that file extensions are user-modifiable metadata and thus unreliable, while magic bytes provide a content-based verification that is independent of the filename.
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
✓
Examining the file's magic bytes
Magic bytes (or file signatures) are unique byte sequences at the beginning of a file that identify its format regardless of the file extension. This method is reliable because it examines the actual binary content, such as the 'PK' header for ZIP files or '‰PNG' for PNG images, rather than relying on user-assigned metadata that can be easily changed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Opening the file in a text editor
Why it's wrong here
A text editor renders bytes as characters, so binary headers appear as unreadable garbage and no authoritative type is derived. It is tempting because it requires no tooling and works for plain-text formats, but magic-number or signature inspection is needed for reliable identification.
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Checking the file extension
Why it's wrong here
The extension is attacker-controlled metadata and can be renamed freely, so it cannot establish true type. It is tempting because operating systems and users rely on extensions for routine association, making it the correct approach only when the file's provenance is trusted and no adversarial tampering is suspected.
- ✓
Examining the file's magic bytes
Why this is correct
Magic bytes are fixed signature values at the start of a file's binary content, so they identify the true format independently of the filename extension. An attacker can rename a malicious executable to .txt, but the magic bytes still reveal the actual type, satisfying the requirement to determine file type regardless of extension.
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Checking the file size
Why it's wrong here
File size reveals nothing about format; a renamed executable and a document can share identical lengths. It is tempting because size is trivially read without parsing content, and it is genuinely useful for spotting appended data, hidden streams or archive-bomb indicators, not for identifying type.
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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.