File overwriting is when new data replaces existing data on a storage device, effectively erasing the original contents. When a file is overwritten, the operating system simply writes the new data over the clusters occupied by the old file. The original data is not actually deleted at that time, but it is eventually overwritten as those disk clusters are reused. Recovering overwritten files is difficult because once new data occupies those clusters, the original contents appear to be permanently gone.
However, there are situations where portions of overwritten files can be recovered. This is because some of the original data may still reside intact in sectors of the disk that were not overwritten. Advanced data recovery software looks at the magnetic traces left on the platters to recover remnant data. But there is no guarantee overwritten files can be restored, and the likelihood declines rapidly with each new write operation. Still, in some cases it is possible to recover previously overwritten files by leveraging data recovery tools and techniques.
How File Overwriting Works
When a file is deleted on a computer, the operating system does not actually remove the file’s data from the hard drive. Instead, it marks the file’s sectors on the disk as available for new data. The original file contents remain intact in those sectors until they are overwritten by new files.
According to http://longforddc.com/can-system-restore-recover-overwritten-files/, when a new file gets written to the disk, it may occupy some or all of the same sectors where the deleted file’s data still resides. As the new data overrides the sectors, the original contents of the deleted file are overwritten bit by bit and permanently destroyed.
Once file contents are fully overwritten, the original data is generally unrecoverable. Overwriting even a portion of a deleted file can make recovery difficult or partial. The more file segments that are overwritten, the less likely recovery becomes.
Understanding this overwrite process at the physical disk level is important for determining if and how deleted files can be recovered before they are fully replaced by new data.
When Overwritten Files Can Be Recovered
In some cases, an overwritten file is still recoverable if the overwrite was not complete. Here are some scenarios where partial file overwrite enables recovery:
If a file was only partially overwritten, the portions that were not overwritten may still be recoverable. For example, if only the first part of the file was overwritten with new data, the later portions of the file may still contain the original data intact (Source: https://www.usenix.org/legacy/event/osdi08/tech/full_papers/anand/anand_html/node41.html).
Some file systems don’t immediately overwrite data blocks when deleting or overwriting a file. The original data may remain intact until those blocks are needed again. This enables recovery of the original overwritten file (Source: https://www.archives.gov/files/applied-research/psc/scalable_lightweight_archival_storage_hierarchy_2_at_marac.ppt).
If a backup or snapshot of the disk was made prior to the overwrite, the original file contents can be recovered from the backup.
Having a drive image or full system backup is useful in case overwritten files need to be recovered.
Data Recovery Software
Data recovery software provides a way to recover overwritten files without relying on backups or version history. The key is using a tool designed to dig deep and scan a drive’s sectors to find traces of deleted or overwritten data. However, not all data recovery apps are capable of recovering overwritten files.
To recover overwritten data, the software needs raw file recovery and sector-by-sector scanning features. This looks at the hard drive’s contents at a low level to find remnants of files even if they have been partially or fully overwritten by new data. Advanced applications like Disk Drill, Stellar Data Recovery, and EaseUS Data Recovery Wizard offer these capabilities. They can often recover previous versions of overwritten Office docs, photos, video files, and more https://www.pandorarecovery.com/blog/recover-overwritten-files/.
Free, open source tools like PhotoRec can also recover overwritten files in some cases. However, paid solutions like Disk Drill tend to offer the best results when attempting a full restore of critical overwritten documents or media files. With the right software, overwritten data can often be recovered, unless the original files have been completely destroyed by repeated, extensive overwrites.
Sending to a Data Recovery Service
If DIY recovery methods don’t work, you may need to turn to a professional data recovery service. These services have specialized equipment and software that can read raw data off a drive to potentially recover overwritten files. The process involves cloning the drive and attempting raw file recovery on the clone, to avoid further modifying the original drive.
Professional data recovery has the best chance of recovering overwritten files if other options have failed. However, it can be expensive, with costs ranging from $300 to over $1000 depending on the service and amount of data. Results aren’t guaranteed, so only use as a last resort for critical lost files.
According to EaseUS, choosing a reputable recovery lab is crucial, as inexperienced technicians could cause further data loss. Research companies thoroughly and look for positive customer reviews.
Tips to Avoid File Overwrites
The best way to avoid needing to recover overwritten files is to prevent overwriting important files in the first place. Here are some tips to help avoid accidental file overwrites:
- Make regular backups of important files and folders. Backups give you a copy to restore from if the original gets overwritten.
- Use versioning systems that save multiple versions of files over time. This allows you to revert to an older version if the latest gets overwritten.
- Be careful when moving files between drives and directories. Accidentally copying a file over an existing one with the same name will overwrite it.
- Use scripts and programs cautiously. Poorly written scripts may overwrite files unintentionally [1].
- Double check before clicking “Save” in your applications. Some programs will overwrite existing files without asking.
- Turn on file permissions to make files read-only. This prevents accidental overwrites.
- Organize files carefully into folders. Keep important files separated from areas with frequent file operations.
Taking preventative measures like these will reduce your risk of needing to recover overwritten data. But accidents still happen, so also be prepared with recovery solutions in case an important file gets overwritten.
Recovering With File Versions/History
Some applications automatically save previous versions of files as you edit them, allowing you to restore to an earlier version if needed. For example, Microsoft Office applications like Word, Excel, and PowerPoint have a feature called AutoRecover that saves different versions as you work. You can access previous versions by right-clicking the file, selecting ‘Version History’, and choosing a version to restore.
Source code editors like Visual Studio and VS Code also track file changes and let you view the edit history. You can usually find options to view historical versions and roll back to an earlier one if you accidentally overwrite the file. In VS Code, you can use the ‘Local History’ command to see previous versions and restore one [1].
Some cloud storage services like Dropbox and Google Drive maintain a history of changes so you can restore previous versions of files. The version history allows you to roll back to before the file was overwritten.
Having regular file backups is another way to recover older versions before an overwrite. You can restore the entire drive from a backup taken prior to the overwrite to get the original files back.
Recovering From a Drive Image
One way to recover overwritten files is by restoring a drive image or system backup that was created before the files were deleted or overwritten. Drive imaging software takes a snapshot of your full hard drive or partitions, saving it as an image file. This image can then be stored as a backup and restored later if needed.
If you have a drive image from before the accidental overwriting occurred, you can simply restore that image to get your original files back. For example, if you image your external hard drive monthly, you could restore last month’s image to recover any files that were overwritten since then. Some popular drive imaging programs that can be used for recovery include Macrium Reflect, Acronis True Image, and Clonezilla.
The key is having a drive image that predates when the files were overwritten. So regularly creating system images or drive backups provides an additional layer of protection against accidental overwrites. Just be sure to store the backup images externally or on cloud storage rather than the same drive you’re imaging.
When File Recovery Isn’t Possible
In some cases, recovering an overwritten file is simply not possible. If the entire hard drive has been formatted or overwritten, it is extremely unlikely that any files can be recovered. A full format erases the entire file system and overwrites the disk with zeros or random data. Once this occurs, the original file contents are essentially gone for good.
According to Stellar Info, “The hard drive recovery from overwritten hard drive is impossible as it is an irreversible process.” https://www.stellarinfo.com/blog/why-it-is-impossible-to-recover-data-from-an-overwritten-hard-drive/
If individual files have been completely overwritten with new data several times over, the chance of recovering anything usable is extremely slim. The more passes of overwriting that occur, the less likely recovery becomes. Once data has been overwritten on an HDD or SSD multiple times, it can be considered permanently lost.
In these extreme cases of complete overwriting, no data recovery software or service will be able to recover the original files. The only option may be to restore from a backup taken before the overwrite occurred. Otherwise, the user must come to terms with the data being unrecoverable.
Conclusion
In summary, recovering overwritten files can be a challenging but achievable process in some cases. The key points are:
- When a file is overwritten, the original data is not completely erased – remnants may still exist that can be recovered.
- Specialized data recovery software can sometimes find and restore portions of overwritten files.
- Sending your drive to a professional data recovery service offers the best chance of recovering overwritten data.
- Having a drive image backup or file version history can allow you to restore a previous version of an overwritten file.
- But if a file is completely overwritten multiple times, the original data may be unrecoverable through any means.
While difficult and not guaranteed, it is sometimes possible to recover overwritten files through the methods discussed here. With the right tools and techniques, you may be able to get back that important data you thought was lost forever.
