Data Recovery Engineering Software

Professional data recovery software
by data recovery professionals

File Listing and Testing Software : Statistical Information
Whilst a file quality test is under way, live statistics are displayed on-screen so you know exactly how the file list is looking.

A typical set of statistics is shown below.

FLT Statistics Section

A breakdown of the statistics show in the software is;

  • Tested : Total files that have currently been tested.
  • Good : Files where the headers match one of those in database.
  • C/Head : No match on existing headers, but matches a common header.
  • Corrupt : File where there are no matches in the database or common headers.
  • Unknown : There are no entries for the extension in the database. (see note 1 below)
  • Skipped : Number of files removed by Skiplist filter.
  • Zero Bytes : File of zero length.
  • Invalid filename : File contains invalid characters due to corruption.
  • Access Errors: Unable to access the file. (See note 2 below)
  • Encrypted : Number of encrypted files found.
  • Small Files : Files less than 512 bytes. (see note 3 below)
  • No ext : Files that have no extension (see note 4 below)

Even where files are marked as corrupt, it may just be that the database needs updating for a few specific extensions.

Notes on the statistics

  1. Unknown or Ambiguous File Types
    These appear when there are no database entries for specific file extensions. There are many ambiguous file extension types; e.g. '.bin' , '.dat' , '.inf' , '.txt' , etc that almost always contain different data from one file to the next.

  2. Access Errors
    These errors occur when there is a problem opening the file for testing. It could be for a number of reasons, the most common are that; it is already open in another application, the file has been blocked by AV software as it is infected, the file is locked using windows security.

  3. Small Files of less than 512 bytes
    The minimum file size that FLT can read is 512 bytes (1 sector). With modern file systems such as NTFS, files of less than approx 900 bytes are actually stored within the MFT record itself and not in the data area on the drive.

  4. Files with no Extension
    Obviously, there can be no entries for files without any extension, but are included in the statistics for completeness.

The Recovery quality is calculated using the following formula. (Good+Common headers)÷(Good+Common Header+Corrupt) x 100

In the example above this gives (21648+20)÷(21648+20+17) x 100 = 99.9 %