Anti-Forensics Field Manual

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Overwriting ======

===== Definition =====
Overwriting is concerned with data that is deleted, partially recoverable, unrecoverable, or left behind in storage areas that no longer belong to an active file.
In a forensic report, overwriting should be treated as a source of evidence and uncertainty, not as a shortcut to intent. The useful question is what the record supports, what it does not support, and what another source says when asked the same question.

===== Background =====
Deleted data is where forensic hope goes to negotiate with storage reality. Sometimes the file is recoverable. Sometimes the SSD has already swept the floor. Sometimes the carved fragment is just a few bytes wearing a convincing hat.
For practitioners, the value is not drama; it is knowing which facts can survive review and which ones need to stay in the notes. Sometimes the file was wiped. Sometimes the SSD did what SSDs do. Sometimes the carving tool came back holding a sleeve and no body.

===== Technical Description =====
The technical work compares allocation state, remnants, metadata, carving output, recovery limits, storage media, and the timing of collection.
If the tool normalized, decoded, or reconstructed the record, that transformation belongs in the notes.

===== Forensic Relevance =====
  * **Contradiction testing:** It is useful for finding places where logs, metadata, storage behavior, or accounts disagree.
  * **Reporting decisions:** It helps decide how narrow the finding should be when overwriting looks interesting but not conclusive.
  * **Timeline reconstruction:** Overwriting can help place activity in sequence when the time source and collection conditions are understood.
  * **Recovery analysis:** It can explain why data was recovered, missed, corrupted, or only partially reconstructed.
  * **User activity review:** It may support account or profile context, but only when independent artifacts point the same direction.

===== Evidence Sources =====
^ Evidence source ^ What it may show ^ Reliability limits ^ What it cannot prove alone ^
| Storage-device behavior | May explain why recovery returns little or nothing. | SSD firmware behavior is often below file-system visibility. | Does not prove deliberate wiping. |
| File-system allocation records | May show deletion or allocation state. | Can be reused or overwritten. | Does not explain motive. |
| Recovery output | Shows what could be recovered under examined conditions. | Depends on tools, timing, and media. | Does not prove data never existed. |
| Collection notes | May record media type, imaging method, errors, and timing. | Weak notes weaken every recovery claim. | Do not replace technical evidence. |

===== Interpretation Limits =====
The most common error is treating overwriting as proof of motive. It may support a technical event, a sequence, or a contradiction, but motive needs stronger ground.
Another bad leap is treating absence as intent. Missing data can come from retention, configuration, collection scope, sync behavior, overwriting, media behavior, or ordinary use.
A tool result should be described as a parsed or recovered record, not as the tool's opinion about what happened. Tools surface evidence; they do not understand it.
A fragment can be useful, but it should not be promoted to witness of the year.

===== Common Misinterpretations =====
  * Ignoring benign explanations because the suspicious explanation is easier to write.
  * Treating recovery failure as proof that evidence was destroyed.
  * Treating one carved fragment like a confession because it fits the preferred story.
  * Ignoring SSD TRIM, overwriting, fragmentation, and collection timing.
  * Reporting a recovered file without explaining carving limits and validation.

===== Example Scenario =====
A reviewer sees storage-device behavior in the case file and asks whether it actually supports the written conclusion.
The artifact may explain part of the sequence, but ordinary system behavior still needs to be ruled in or out.
The analyst preserves the source, exports the relevant records, checks file-system allocation records, and documents what remains unresolved.

===== Analysis Workflow =====
  - Define the question before opening another parser: what should Overwriting help answer?
  - Preserve the source evidence and document how the storage-device behavior was collected.
  - Record tool versions, input paths, output paths, time settings, and errors.
  - Identify observed facts before writing any interpretation.
  - Normalize time sources and document timezone, clock drift, and collection-time effects.
  - Compare at least two independent artifact families before raising confidence.
  - Consider benign explanations, automated behavior, retention, sync, and storage-device behavior.
  - Write conclusions proportionally: observed fact first, inference second, uncertainty always visible.

===== Reporting Guidance =====
Reporting on overwriting should be precise enough that another analyst can retrace the claim without inheriting the original examiner's confidence.
Avoid wording that converts possibility into intent. The report should not say a user deliberately deleted, hid, wiped, or tampered with evidence unless the evidence actually supports that conclusion.
Report-ready wording:
  * The available storage-device behavior is consistent with activity related to overwriting, but it does not independently establish motive or user intent.
  * Recovery was limited under the examined conditions; additional corroboration would be required before concluding deliberate destruction.
  * The finding should be read with the collection scope, time-source limits, and alternate explanations described in this report.

===== Confidence and Reliability =====
^ Confidence level ^ What it looks like for this topic ^ How to report it ^
| Low | Storage-device behavior exists, but collection scope, time source, or surrounding context is limited. | State the observation and keep interpretation narrow. |
| Moderate | Storage-device behavior aligns with File-system allocation records, but attribution or intent remains unresolved. | Say the artifacts support the finding, not that they prove it. |
| High | Multiple independent sources agree on sequence, source system, account context, and collection conditions. | Use stronger language, but still separate observed facts from inference. |

===== Related Concepts =====
  * [[wiki:digital_forensics:file_systems:carving_false_positives|Carving False Positives]] - Helps keep the finding grounded in a wider evidence pattern.
  * [[wiki:digital_forensics:file_systems:data_remanence|Data Remanence]] - Often appears nearby in reviews of the same system or behavior.
  * [[wiki:digital_forensics:file_systems:deleted_files|Deleted Files]] - Helps keep the finding grounded in a wider evidence pattern.
  * [[wiki:digital_forensics:file_systems:file_carving|File Carving]] - Useful when checking whether another artifact supports the same interpretation.
  * [[wiki:digital_forensics:file_systems:recycle_bin_artifacts|Recycle Bin Artifacts]] - Helps keep the finding grounded in a wider evidence pattern.
  * [[wiki:digital_forensics:file_systems:slack_space|Slack Space]] - Often appears nearby in reviews of the same system or behavior.

===== Tools =====
  * [[https://www.autopsy.com/|Autopsy]] - Case review, file-system browsing, timelines, term search, and recovered artifact review.
  * [[https://www.sleuthkit.org/sleuthkit/|The Sleuth Kit]] - Command-line file-system analysis and evidence inspection.
  * [[https://www.cgsecurity.org/|PhotoRec and TestDisk]] - File recovery and partition recovery utilities.
  * [[https://foremost.sourceforge.net/|Foremost]] - File carving by headers, footers, and simple signatures.
  * [[https://github.com/sleuthkit/scalpel|Scalpel]] - Configurable file carving utility.
  * [[https://github.com/simsong/bulk_extractor|bulk_extractor]] - Feature extraction from disk images without relying on file-system allocation.
  * [[https://www.exterro.com/ftk-product-downloads|FTK Imager]] - Forensic imaging, preview, and export workflows.
  * [[https://guymager.sourceforge.io/|Guymager]] - Linux forensic imaging with hashing and acquisition logs.
  * [[https://sourceforge.net/projects/dc3dd/|dc3dd]] - Disk imaging and hashing utility.
  * [[https://www.gnu.org/software/ddrescue/|GNU ddrescue]] - Imaging damaged media while preserving recovery logs.
  * [[wiki:tools:start|Forensic Tools]] - Full tool directory for the wiki.

===== Limitations of Tools =====
Tools parse, surface, and organize evidence. They do not create conclusions.
Parser output can be affected by version differences, unsupported formats, corrupted records, timezone handling, partial collection, and storage behavior outside the tool's view.
When a tool produces a strong-looking result, validate it against another tool or source where the stakes justify it. A parser can recover a fragment; it cannot tell you whether the fragment deserves a paragraph in the report.

===== References and Further Reading =====
  * [[https://learn.microsoft.com/en-us/windows-server/storage/file-server/ntfs-overview|Microsoft NTFS overview]] - NTFS technical reference.
  * [[https://www.sleuthkit.org/sleuthkit/docs.php|The Sleuth Kit documentation]] - File-system analysis documentation.
  * [[https://www.nist.gov/itl/ssd/software-quality-group/computer-forensics-tool-testing-program-cftt|NIST CFTT]] - Tool testing context.
  * [[https://csrc.nist.gov/publications/detail/sp/800-86/final|NIST SP 800-86]] - Guide to integrating forensic techniques into incident response.
  * [[https://www.forensicfocus.com/articles/what-is-digital-forensics/|Forensic Focus: What is digital forensics?]] - Practitioner-facing overview.

===== See Also =====
  * [[wiki:digital_forensics:file_systems:start|File Systems]]
  * [[wiki:digital_forensics:file_systems:carving_false_positives|Carving False Positives]]
  * [[wiki:digital_forensics:file_systems:data_remanence|Data Remanence]]
  * [[wiki:digital_forensics:file_systems:deleted_files|Deleted Files]]
  * [[wiki:digital_forensics:file_systems:file_carving|File Carving]]
  * [[wiki:digital_forensics:file_systems:recycle_bin_artifacts|Recycle Bin Artifacts]]
  * [[wiki:digital_forensics:file_systems:slack_space|Slack Space]]
  * [[wiki:digital_forensics:file_systems:ssd_trim|SSD TRIM]]
  * [[wiki:digital_forensics:file_systems:trash_folders|Trash Folders]]
  * [[wiki:digital_forensics:file_systems:unallocated_space|Unallocated Space]]
  * [[wiki:digital_forensics:file_systems:alternate_data_streams|Alternate Data Streams]]
  * [[wiki:tools:start|Forensic Tools]]
  * [[wiki:resources:start|Project Resources]]

===== Reader Takeaway =====
Overwriting is useful when it helps explain what the evidence can support and where the limits begin. Treat overwriting as one part of a corroborated record, not a shortcut to intent. Sometimes the file was wiped. Sometimes the SSD did what SSDs do. Sometimes the carving tool came back holding a sleeve and no body.

===== Use Notes =====
This article is for defensive education and technical reference. It should not be treated as legal, forensic, investigative, compliance, or operational advice without qualified professional judgment.