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Datei-Shredder
In brief
A file shredder is a program that not only deletes individual files or folders but first overwrites their storage space so that they cannot be recovered. It is suitable for targeted deletion during ongoing operation. For decommissioned devices in companies it is not enough, because copies, caches and hidden areas of the data carrier remain untouched.
How a file shredder works
With normal deletion, the operating system removes only the reference to the file. The content stays on the data carrier until it happens to be overwritten. A file shredder overwrites the occupied areas deliberately, often with random data and, if desired, multiple times (Overwriting). Afterwards it removes the file.
Limits in practice
- SSDs and flash: The controller writes new data to other locations. Overwriting a file therefore does not reliably hit the original memory cells. Functions such as TRIM additionally alter the behavior.
- Copies: Temporary files, thumbnails, page files, shadow copies, backups and cloud synchronization often contain further versions.
- No proof: A file shredder does not prove that a device is free of data.
For decommissioning entire devices, it is therefore customary to erase the whole data carrier with certified software and a report. Second IT erases hard drives, SSDs and mobile devices with Blancco and issues a digitally signed erasure certificate for each device. Why formatting and simple deletion are not enough is shown in the guide Securely erasing hard drives and SSDs.
Frequently asked questions about the file shredder
How do I delete files securely?
For individual files on hard drives, a file shredder can help. On SSDs this is unreliable. Anyone handing over an entire device should erase the complete data carrier using a suitable method and document the result.
Is the recycle bin enough for deleting?
No. Even after the recycle bin is emptied, the contents usually remain on the data carrier and can be recovered with simple programs.
How often does a file shredder have to overwrite?
For modern hard drives, one pass is generally considered sufficient. Multiple overwriting brings hardly any additional security but does not solve the problems with SSDs and copies.
Does a file shredder also work on SSDs?
Only to a limited extent. An SSD’s controller writes new data to other locations, so overwriting does not reliably hit the original memory cells. Functions such as TRIM additionally alter the behavior. A file shredder is therefore unreliable for SSDs.
Why is a file shredder not enough for decommissioned devices?
It affects only individual files. Copies, caches, shadow copies and hidden areas of the data carrier remain untouched. It also provides no proof. When decommissioning, the entire data carrier is therefore erased with certified software and a report.
Erase entire devices instead of individual files, with certification.
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