File Carving: An Essential Method for Data Recovery and Digital Forensics 

Introduction to File Carving 

File carving is a critical process in the field of data recovery and digital forensics. It refers to the method of recovery or reconstructing excluded or formatted files from a storage medium. In simpler terms, file carving is the act of researching a data flow, locating file fragments, and reconstructing files that may no longer be accessible through conventional file management systems. The importance of file carving is particularly evident in the field of digital forensic. Forensic experts often need to recover deleted, corrupted or absent files during investigations, especially when these files maintain vital evidence. If a file was accidentally deleted, the system has been formatted or a file system has been corrupted, file carving techniques can help extract valuable data that can be crucial for forensic investigation. This process plays a key role in investigating cybercrimes, where excluded file recovery usually leads to the discovery of important evidence, such as and email, documents, images or even malicious files that can help create a case. In this blog, we will delve deeper into the concept of file sculpture, as it works, the different methods employed in the file carving and the tools that enable it. 

How File Carving Works 

File carving works by researching recognizable patterns, called “File Subscriptions” within the data on a storage device. It can be compared to the act of looking for pieces of a break -in, with the objective of recovering these pieces and rebuilding the original file. This process becomes especially useful when file metadata (such as file names, directories, and other file system information) is absent or corrupted. File carving can recover deleted files by examining gross data on the disk. Even if a file has been deleted, the actual data may still be present in the space not allocated or free. When files are deleted, they are usually removed from the file system index, but the data itself can remain on the disk until it is replaced by new data. Several techniques are used, depending on the file type and how data is stored. The most common techniques are the carving of the header, the carving based on the file structure, and the content-based sculpture.  

Let’s take a closer look at these methods: 

Common file carving techniques  

Header-Footer or Header-Maximum File Size Carving 

Header size carving or maximum header One of the most widely used methods in file carving is based on the principle that many types of files have unique identifiers on their headers and baseboards. These identifiers are known as magical numbers and are a fixed sequence of bytes that help distinguish one file format from another. 

For example: JPEG image files usually start with the FF D8 header and end with the FF D9 footer. When researching these specific sequences, a tool can identify and create a JPEG file from gross data, even if the file is deleted or corrupted. In cases where the header and footer are not enough to identify the file type, some tools depend on the maximum size of the file. Using the maximum size of a file type (such as the known size of a typical image file), the tool can try to recover the entire file, even if only part is accessible. 

File Structure-Based Carving 

Carving based on file structure In this technique, file carving goes one step further, analyzing the internal structure of a file. Many file formats, such as PDFs, images, and videos, follow specific internal layouts that include headers, baseboards, metadata and other specific file identifiers. For example, an image file can have a recognizable structure with a specific set of bytes at defined intervals. By understanding how a specific file type is structured, file carving tools can search through the gross data of a disk and locate fragments that correspond to these known structures, even if the file has been partially replaced or deleted. The success of this method depends on having a solid understanding of the file structure that is being directed. This is why forensic experts often need to rely on specialized software and techniques that can automatically detect and extract these file components. 

Content-Based Carving 

Content-based carving differs from the carving based on the header structure and file structure as it analyzes the content within the file itself. This method does not depend on the structure or internal signature of the file but focuses on identifying specific content characteristics and patterns that may suggest the presence of a recoverable file.  

Some of the content -based carving techniques include:  

Character count: Looking at the character count and standards in the data, tools can identify if data can represent a text-based file (such as an HTML document or log file). 

 Text/Language Recognition: Some tools are designed to recognize the set of languages or characters used in a file, helping to determine if certain parts of the data belong to a specific file type.  

White and Black Data List (filters): When applying filters, certain data types can be deleted from the recovery process, which helps focus on the most relevant or potential files.  

Statistical Attributes: Tools can use statistical analysis to predict the likelihood that a data part belongs to a specific file type.  

Information Entropy: This method involves the analysis of data randomness or predictability, which can help detect certain file types, particularly compressed files or encrypted data. 

Semantics-Based Carving 

Although not as commonly used as other methods, semantics-based carving focuses on identifying files based on their meaning or content, not its structure. This may involve looking for phrases, keywords or known patterns that are consistent with specific file types (such as documents, emails or database inputs). However, this method is more complex and less universally applicable than other carving techniques. 

File Carving using NBFTools TRIOS

File Carving:

This option is used for recovering complete files from any data source. It 

is particularly helpful when there is a need to extract files that may have been removed, fragmented, or hidden within the data. 

NBFTools TRIOS Carve feature supports the following types of files: 

• Images — PNG, JPEG, JPG, TIFF, ICO, HEIC, WEBP, GIF, 

• Office Document — PDF, DOCX, PPTX, XLSX, ODS etc. 

• Miscellaneous Files — HTML, ZIP, EMLX, VID, SQLITE, MSG, REGISTRY etc. 

• Audios & Videos — MP4, 3GP, AVI, MOV, MP3, VOB, MIDI, WAV etc. 

Data Carving:

With this option, examiners can recover specific types of information, such as email addresses, social security numbers, URLs, and other structured data.  

Conclusion  

File carving is an essential skill and technique in digital forensics, providing researchers with the ability to recover and reconstruct excluded or missing files. Be used to collect evidence in cybercrime investigations or to restore important data, file carving allows forensic experts to explore gross data on a storage device and extract valuable information that could otherwise be lost. Using methods such as header sculpture, file structure -based carving and content -based sculpture, experts can adapt their approach to the recovering data type. With the help of powerful tools and a deep understanding of file formats and structures, file carving remains an invaluable process for discovering hidden data and solving digital mysteries.