How secure erasure works
Secure erasure means overwriting the contents of a file or a drive before the space is released, so that no recovery program can reconstruct the data. O&O SafeErase does this for files, folders, traces, free space and entire drives.
What normal deleting leaves behind
When Windows deletes a file or empties the Recycle Bin, it only removes the reference to the file in the file system and marks the space as free. The contents stay on the drive until other data happens to overwrite them. Recovery programs read exactly these areas.
Remnants are also left in places you do not see directly:
| Remnant | Where it is |
|---|---|
| Free space | Contents of files that were deleted normally, for example before O&O SafeErase was installed. |
| Cluster tips | Unused space at the end of the last cluster of an existing file. It can contain parts of older files. |
| File system entries | Names, sizes and dates of deleted files in the Master File Table (MFT) of an NTFS drive. Very small files are stored in the MFT entirely. |
| Traces | Browser history, cookies, cache, temporary files, thumbnails, memory dumps and the Recycle Bin. |
What O&O SafeErase does
O&O SafeErase overwrites the data with the selected erase method and then deletes it. Depending on the task, it treats different areas:
- Files and folders and traces: the contents of the selected objects.
- Free space: free areas, cluster tips and MFT entries of a drive. Existing files are kept.
- Drives and partitions: every sector of the selected partition or disk, including all files.
- Entire PC: all internal disks including Windows, started in Fortress Mode.
After the erasure, a report lists the treated objects, the method actually used and any warnings. A signed erasure record documents the result.
Limits
- Secure erasure cannot be undone. Data that has been overwritten cannot be restored, not even by O&O Software.
- Copies of a file in backups, cloud storage, e-mail attachments or on other drives are not affected. Erase them separately.
- A file that another program keeps open cannot be erased. The report names it with a warning.
- On SSDs, the controller decides where data is physically written. Software can only overwrite the areas that Windows can address; see Erase methods and SSDs.