What is File Carving and Its Basic Techniques

What is File Carving?

File Carving is a popular way to get files back from computer memory by using details about their content and structure instead of the file system. This method is very important for digital forensics investigations because it lets you get back files by looking at their text and structure. Getting structured information from raw data based on format-specific properties found in the structured data is what this broad term refers to.

The Problem of Destroyed or Deleted Data

There are several reasons why files might get deleted. Any of these things can happen by mistake, as part of an attack, or on purpose to hide proof. When you delete a file, the data stays on the disc, but the record in the file system metadata is generally gone too. File carving can be used to get back data from a hard drive where the information has been wiped or damaged in some other way. This method might still work on a disc that has been cleaned or re-partitioned.

Why Are Forensic Investigations Needed?

In more complicated crime cases, forensic studies into computers and computer data are becoming more and more important. Often, proof of wrongdoing can be found in computer files, but thieves may try to hide or get rid of these to avoid being caught. Criminals are hiding more and more things, from pictures that could be used against them to financial records that could be used as evidence in court. Computer forensic experts have a lot of tools that can help them get these papers out of the computer and put them back together again.

Information-Based Retrieval

All computer-based filing systems include some information that specifies the actual file system. This is known as metadata. At the very least, this comprises the folder and file hierarchy, as well as their respective names. The file system information will also keep track of the physical locations on the storage device where each file is stored. 

Even in cases when the file system metadata is lost or destroyed, forensic computer scientists can retrieve and recover deleted, corrupted, or concealed files from a storage device by using the file carving approach. In the course of a potentially criminal inquiry, this enables them to recover important digital evidence that could otherwise be lost.

One of the main tools that forensic computer scientists use to identify and access hidden data is known as "file carving". This tutorial looks at what file carving is, and how it is used to help trap criminals or rebuild information that has been lost to a malicious act.

Tools Used for File Carving

The main tools used for file carving are as follows -

• Header/Footer carving. This common tool looks for certain byte sequences at the beginning (header) and end (footer) of a file to determine where its limits are and get the data inside them.
• File Structure Carving. Using recognisable patterns in the data stream, this method examines the internal organisation of a file format in order to locate and recreate the file.
• Maximum file size carving. This method looks for possible file headers inside a given byte range in an effort to recover files based on a pre-determined maximum file size.
• Structure-based carving. The tool finds patterns in file content, such as picture compression methods or text sequences, to recover files without header information.

System Specifics

Most modern file systems, like the UNIX Fast File System (FFS), and the 32-bit File Allocation Table (FAT32)work with groups - known as "clusters" - that are all the same size. One example of this would be a FAT32 file system that is split up into groups of 4 KiB, where 4KiB is 4,096 bytes of information. Every cluster has exactly one file, and each cluster never has more than one file. Each file is less than 4 KiB. Many groups are given files that are bigger than 4 KiB. Sometimes these groups of data are all connected, and other times they are spread out over two or more appropriately-named "fragments." Each fragment has a number of connected groups that store a different part of the file's data.

File Carving Software Examples.

There are a number of well-designed bespoke programs that are used by professionals to carve files for forensic and investigative purposes. While there are many tools available tools, amongst the current best are:

• Autopsy. This is an open-source tool that is regarded as being among the easiest to use while being able to handle complex tasks. It is able to rebuild data from almost no inputs and can recover files even if the information for the file system has been lost or deleted. Autopsy is capable of performing a variety of tasks, including the analysis of file information, the traversal of file systems, and the generation of timelines, in addition to the recovery of deleted data. It is particularly effective in digital forensics cases that necessitate retrieving a significant amount of data due to these capabilities.
• SalvationDATA. This is a tool that it routinely used by professional agencies for data repair and reclamation. It has an array of powerful yet easy-to-use tools that can reconstruct data from almost no input. It has two important features, being its Data Recovery System (DRS) and Database Forensics (DBF). The DRS does not rely on file system metadata, making it appropriate for forensic investigations in which the file system has been interfered with or damaged. The DBF is expert at building information from damaged databases, allowing it to gather information from systems that have been hacked.
• Foremost. This is another powerful open source program that can get data back from a number of different file systems. Foremost is a program that was primarily made to retrieve files from raw picture information, but it also excels at rebuilding information from a range of file types. Foremost can recover traces of files from a damaged or formatted storage media by analysing its underlying structure. This method is particularly efficient for retrieving documents, photos, and many file types that have been erased or lost due to disc damage.
• PhotoRec. While this forensics tool can extract data from almost any filetype, it was designed to rebuild pictures from damaged information. In contrast to other available programs, PhotoRec simply concentrates on the underlying data, avoiding the file system entirely. In forensic investigations, this method is essential, particularly when working with broken or damaged file systems when conventional recovery techniques are ineffective. Digital cameras, hard discs, CDs, and even computer memory cards may all have their files recovered with PhotoRec's free data carving tools.
• Scalpel. Regarded as one of the earlier tools developed for data analytics and recovery, Scalpel has grown to be one of the most powerful yet easy to use tools. This open-source software has an array of sub-tools that can examine and rebuild even heavily damaged file systems. The Scalpel file carver can identify a wide range of file formats. It doesn't matter what filesystem the disc was formatted using. Scalpel traces files using a database that includes headers and footers for various file kinds.

Problems with File Carving

Data carving has several advantages - not least that it can help restore lost files - but it is not without its share of drawbacks. Due to the lack of file system metadata, data must be identified only by their defining features. This might result in incomplete or corrupted file recovery.

In addition to requiring powerful computing resources, the procedure necessitates sophisticated tools that can distinguish between various file formats and verify the accuracy of the recovered data.