How Recuva Works: File System-Level Data Recovery
Logical deletion and residual metadata. When a file is deleted, the operating system does not physically overwrite the clusters it occupies — instead, the corresponding entry in the volume's metadata structure is modified (an $MFT record in NTFS, or an element of the FAT/exFAT table), where the cluster chain is marked as free and the first character of the file name is replaced with a service marker. Recuva performs low-level parsing of these data structures — the Master File Table, Index Allocation, and $DATA attributes — reconstructing the file's logical continuity up to the point at which its sectors are actually overwritten with new data.
Signature analysis and carving. In cases where metadata has been irrecoverably lost (formatting, file table corruption, a RAW volume layout), the application switches to deep scan mode — a sector-by-sector read of the media that bypasses the file system, identifying data by the binary header and footer signatures (magic numbers) characteristic of specific container formats. This approach, known as file carving, allows intact objects to be extracted even in the complete absence of a file system, though it does not guarantee recovery of correct file names or directory hierarchy.
Integrity and fragmentation assessment. Before recovery, Recuva performs a heuristic assessment of the cluster chain's state, comparing the volume's allocation map against the file's expected size to detect fragmentation and partial overwriting. The result is classified using a preservation indicator (excellent/poor/unrecoverable), which accounts for the degree of cluster contiguity and the likelihood of collision with newly written data.
Working with journaling file systems. When analyzing NTFS, Recuva additionally references the $LogFile transaction journal and the $UsnJrnl change journal, which record operations on the file structure independently of the main MFT. Cross-referencing journal entries with the volume's current state allows recovery of metadata for files whose MFT records have already been reused by the system for new objects, as well as partial reconstruction of rename and move history.
Handling alternate data streams. For NTFS volumes, the application accounts for Alternate Data Streams ($DATA:stream_name) attached to the primary file record, which is critical when recovering objects marked with a zone of origin (Zone.Identifier) or containing additional attributes stored outside the main data stream.
Working with solid-state drives and the TRIM command. On SSDs with active TRIM support, the controller is immediately notified that logical block addresses (LBAs) have been freed after file deletion, which triggers internal garbage collection and physical erasure of NAND cells before a recovery program even accesses the volume. Under these conditions, Recuva can rely solely on surviving file system metadata, since the actual cluster contents at the hardware level may already be irreversibly lost.
Safe data extraction. Recovered content is copied byte-by-byte to a destination area physically isolated from the source volume, which prevents overwriting of sectors not yet processed but still potentially recoverable. Additionally, a Secure Overwrite function is implemented, following standards comparable to DoD 5220.22-M, used to guarantee destruction of residual data after confirmed recovery.
