When a file is deleted from a computer’s hard drive, many users assume the file is gone forever. However, that is often not the case – deleted files can frequently be recovered. Understanding what happens to files when they are deleted and whether they can be recovered is important for several reasons.
First, being able to recover deleted files provides a safety net in case of accidental deletion. If you or someone else inadvertently deletes an important file, recovery software may be able to get it back. This can save from potentially disastrous data loss.
Additionally, knowing how file deletion and recovery works is key for properly securing or removing sensitive information. When disposing of old computers or drives, steps need to be taken to ensure personal files cannot be restored. On the other hand, data recovery techniques allow investigators and forensic experts to access deleted evidence.
Finally, understanding file deletion gives insight into how computer storage works on a deeper level. It reveals what’s actually happening when you seemingly remove a file versus fully overwriting it. This knowledge empowers users to better manage their data.
File Deletion Basics
When a file is deleted on a computer, the operating system does not actually erase the data contained within the file right away. Instead, it simply removes the file’s entry from the file allocation table (FAT), which is the directory structure used to keep track of where files are stored on the hard drive [1]. The space on the hard drive that the file once occupied is then marked as being available for new data to be written over it. Until new data overwrites the old file data, it is still present on the physical drive.
So in essence, “deleting” a file simply removes the pointers to its data. The actual contents of the file remain on the drive and could theoretically be recovered until that space is reused for new files. This allows deleted files to often be “undeleted” using recovery software until the original data is overwritten. At the basic level, deleting files is about removing references to the data, not erasing the data itself [2].
File Content After Deletion
When a file is deleted on a computer, the reference to that file’s data on the hard drive is removed from the file system index, but the actual content remains on the hard drive until it is overwritten by new data. The space occupied by the deleted file is now considered available and can be overwritten at any time.
When a file is deleted, its entry in the file table is simply marked as unallocated space or free space. The data itself remains intact in the same physical location on the hard drive where it was previously stored, until it is eventually overwritten by new data.
This is why it’s often possible to recover deleted files using data recovery software, as long as the original data has not yet been overwritten. The software scans the hard drive and looks for files that have been marked for deletion but still have intact data that can be resurrected.
In essence, “deleting” a file simply removes the indexing or pointers to the data, but not the data itself. The data remains in place until replaced by new data written to the same physical location on the storage medium. This allows for undeletion as long as the original data remains accessible and uncorrupted.
According to Apto Solutions, overwritten data is difficult to recover, which is why permanent deletion requires overwriting the data’s physical location on the disk multiple times to prevent data recovery.
Finding Deleted Files
Deleted files can often be recovered as long as they have not been overwritten by new data on the hard drive. When a file is deleted, the reference to the data is removed from the file system, but the actual data itself remains on the drive until it is overwritten. This makes it possible to recover deleted files using file recovery software as long as the original data still exists.
There are many powerful file recovery programs available that can scan a drive and rebuild the file system to make previously deleted files accessible again. Some popular recovery software options include Recuva, EaseUS Data Recovery Wizard, and Restore Previous Versions in Windows. These tools can recover files that were deleted from the Recycle Bin, from external drives, or even after a system crash.
Recovery software scans the hard drive and retrieves file data from sectors that have not yet been overwritten. The more the drive is used after deletion, the greater the chance that critical file data will get overwritten and be unrecoverable. Therefore, for the best chance of recovering deleted files, it is advisable to install and run a file recovery tool as soon as possible after deletion and before continuing to use the drive.
Preventing File Recovery
There are several techniques that can be used to prevent the recovery of deleted files. One of the most effective is file shredding. File shredding overwrites the data in a file multiple times to ensure it can’t be recovered. Tools like Eraser and EaseUS BitWiper can shred files and make recovery virtually impossible.
Other prevention techniques include encrypting files before deletion, which scrambles the data, and physically destroying the storage device. For maximum security, users can combine multiple techniques like encryption and physical destruction to prevent any chance of recovery.
The key is overwriting the raw data on the disk so it can’t be reconstructed. Simply deleting a file normally just removes the file’s entry in the file table, but doesn’t touch its actual contents on disk. To prevent recovery, the raw data itself must be overwritten or destroyed.
When Files Are Overwritten
Deleted files remain on the hard drive until the space they occupy is overwritten by new data. When a file is deleted, the operating system simply marks the space that file occupied as available for new data. The original data remains there until it gets overwritten.
Overwriting happens gradually over time as new files are saved to the hard drive. The operating system allocates available disk space to store new files, filling in areas marked as available when files were deleted. Eventually, the new data writes over the spaces where deleted files were stored.
According to Minitool, there is no fixed timeframe for when overwritten happens. It depends on how much new data you add to the drive over time. The more data you write to the disk, the sooner deleted files will get overwritten with new information. On a frequently used system, files could get overwritten in days or weeks. On a rarely used disk, traces of deleted files may still exist for months or years before getting overwritten.
SSDs vs. HDDs
There are some key differences in how deleted files are handled on solid-state drives (SSDs) compared to traditional hard disk drives (HDDs). When a file is deleted on a HDD, the reference to that file in the file system is removed, but the actual data remains on the disk until it is overwritten by new data. This makes it possible to recover deleted files from a HDD using data recovery software.
SSDs work differently. When a file is deleted on an SSD, the reference is removed from the file system and the SSD controller marks the blocks containing that file’s data as erased. The blocks are not actually erased right away though. Instead, the SSD relies on a process called TRIM to perform garbage collection and securely erase deleted blocks. The TRIM command allows the operating system to tell the SSD which blocks of data are no longer needed. The SSD can then permanently delete these blocks to make space for new writes.
Without TRIM enabled, deleted files on an SSD will remain recoverable until the blocks get reused. With TRIM, the deleted data is rapidly made unrecoverable as soon as it is trimmed by the controller. This makes data recovery more difficult on SSDs compared to HDDs if TRIM is active (source).
Secure Deletion
To prevent deleted files from being recoverable, there are secure deletion techniques that can be used. One method is to use secure deletion software like Eraser or file shredder on Windows PCs. These overwrite the disk space used by the deleted files to make recovery nearly impossible.
Another technique is degaussing, which applies a strong magnetic field to the hard drive to disrupt and erase the data. This makes previous data unrecoverable even by advanced forensic methods. However, degaussing renders the hard drive unusable afterwards.
Users can also choose to encrypt their files when saving them initially. This means the files are encoded and require a decryption key to be accessed. Deleting an encrypted file effectively deletes the ability to decrypt it in the future.
Overall, secure deletion requires overwriting files, degaussing the disk, or encrypting data to prevent recovery when deleted. This gives users peace of mind knowing their deleted files cannot be restored.
Recovering Lost Files
Recovering accidentally deleted files is possible in many cases if you act quickly and use the right recovery methods. Here are some tips for recovering recently deleted files:
First, check your computer’s recycle bin or trash folder. When you delete files, they may go to a temporary holding folder before being permanently erased. You can often restore deleted files from here if they’re still available.
If the file is no longer in the recycle bin, try using recovery software. Programs like RStudio can scan your hard drive and recover deleted files and folders. This is most effective if you run the software immediately after deletion, before the files are overwritten.
You may also be able to restore from a previous version or backup. Windows has a Previous Versions feature that can recover older copies of your files. Or if you routinely back up your computer, you may be able to restore the lost file from your most recent backup.
If the file was stored on an external or removable drive like a USB stick, stop using the device immediately. Continuing to use the drive makes permanent data recovery more difficult. Consult a data recovery service to securely restore the lost data.
Prevention is also key. Be very careful when permanently deleting files. Avoid relying solely on the Recycle Bin, and make regular backups of important files.
Conclusion
To summarize, while deleted files seem to be erased, in reality they are still present on your hard drive until the space they occupy gets overwritten by new information. Their data remains intact immediately after deletion, so deleted files can easily be recovered with the right tools as long as they haven’t been overwritten. The only way to prevent data recovery is to completely overwrite the space, though with SSDs this becomes more complex. To permanently and securely erase files beyond recovery on any device, special software tools for secure deletion should be used. So in conclusion, yes – deleted files do remain saved on your hard drive, lingering invisibly until the space they occupy gets overwritten by new data.
