The correct indication is that the file has slack space which may contain remnants of previously deleted data. This is because the difference between the resident data size of 900 bytes and the allocated size of 1024 bytes represents the unused portion of the cluster, known as slack space, where residual data from prior file allocations can persist. On the Computer Hacking Forensic Investigator CHFI exam, this concept tests your understanding of NTFS file system forensics, specifically how the $DATA attribute reveals the disparity between logical file size and physical cluster allocation. A common trap is confusing slack space with file fragmentation or assuming all allocated bytes contain active data; remember that slack space is a forensic goldmine for recovering hidden evidence. For a quick memory tip, think of slack space as the “leftover room” in a cluster—if the file doesn’t fill the entire allocated block, whatever was there before might still be lurking.
CHFI Storage Forensics and File System Analysis Practice Question
This CHFI practice question tests your understanding of storage forensics and file system analysis. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 investigator notes that a file on an NTFS volume has a resident data size of 900 bytes, but the $DATA attribute lists an allocated size of 1024 bytes. What does this indicate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The file has slack space that may contain remnants of previously deleted data
The difference between actual data size and allocated size is slack space. The file was allocated a cluster of 1024 bytes, but only 900 bytes are used, leaving 124 bytes of slack space that could contain residual data.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 file is compressed using NTFS compression
Why it's wrong here
Compression would change the allocated size, not create slack.
✓
The file has slack space that may contain remnants of previously deleted data
Why this is correct
The difference is slack space; could contain old data.
Related concept
Static NAT maps one inside address to one outside address.
✗
The file's data is stored in the MFT as a resident attribute
Why it's wrong here
Resident data is stored within the MFT record, not allocated clusters.
✗
The file is stored in an alternate data stream
Why it's wrong here
ADS would be a separate stream; slack is within the allocated space.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CHFI question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CHFI NAT questions on configuration and troubleshooting.
Storage Forensics and File System Analysis — This question tests Storage Forensics and File System Analysis — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The file has slack space that may contain remnants of previously deleted data — The difference between actual data size and allocated size is slack space. The file was allocated a cluster of 1024 bytes, but only 900 bytes are used, leaving 124 bytes of slack space that could contain residual data.
What should I do if I get this CHFI question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CHFI NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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