What is a Master File Table?

Pre-requisites: File Systems in Operating System

The Master File Table (MFT) is a system file in the NTFS file system (having the name $MFT) that stores metadata information about all files and directories on an NTFS volume. The MFT acts as an index to all the files and directories on the volume, providing quick access to the information needed to retrieve a file.

Each file and directory on an NTFS volume has a unique record in the MFT, known as an MFT entry. The MFT entry contains information such as the file name, timestamps, permissions, and a pointer to the file’s data. The corresponding MFT entry is updated when a file is created or modified.

When a file is deleted, the corresponding MFT entry is marked as free, but the actual file data remains on the disk until it is overwritten by new data. This can be useful in data recovery scenarios, as the deleted file’s data may still be recoverable. Successful data recovery requires that the Disk regions occupied by the deleted data are not overwritten. 

Note: The MFT is stored on the NTFS volume and is an important component of the NTFS file system. The MFT must remain intact and undamaged for the file system to function properly.

Structure of MFT Record

The structure of the Master File Table (MFT) in the NTFS file system is complex and consists of multiple records, each of which represents a file or directory on the NTFS volume. Each MFT record is 1024 bytes, making the MFT very simple to parse. An MFT record has the following general structure:

• File Record Header: This section contains information about the record itself, including the size of the record, the offset of the update sequence, and the flags that indicate the state of the file or directory.
• File Attribute List: This section contains a list of attributes that describe the file or directory, including its name, timestamps, size, and data. Each attribute is stored as a separate structure with its format.
• Data Runs: This section describes the location of the file or directory’s data on the disk. The data runs are stored as a series of extents describing the starting cluster and the length of each contiguous data block.

The exact format and structure of the MFT in NTFS can vary depending on the version of the file system in use. However, the general structure remains the same, with the File Record Header, File Attribute List, and Data Runs being the main components of each MFT entry.

Tools For Parsing a Master File Table

The Master File Table (MFT) is a system file in the NTFS file system and is not intended to be directly accessed or viewed by users. There are, however, tools that can be used to read the contents of the MFT, including:

• DiskInternals NTFS Recovery is a commercial tool that can recover deleted or damaged files by accessing the MFT.
• HxD is a free hex editor that can view the raw data of the MFT and recover files.

Note: It’s important to note that accessing the MFT directly can be dangerous and potentially lead to file system corruption or data loss. Before attempting to access or modify the MFT, it’s recommended to perform operations on a backup of the MFT or back up important data beforehand.