"Can shredder files be recovered?" is something our users ask us all the time because they're concerned that even using a file shredder to delete sensitive data is not enough. In this article we'll explain how shredding files works, how's it different from simply deleting files, and when and what you should shred.
When we refer to digital file shredding, the actual data isn't shredded. But the analogy with old-school paper shredders is a good one because digitally shredded files become unreadable. When a file is deleted with the help of a shredding app, it's overwritten with random data or a set of predefined characters from one to several times. The more overwrite passes there are, the more securely the file is deleted.
Research done by several data recovery software publishers states that overwriting files in one pass is an effective method of erasing it. This means that consumer-level file recovery apps can't undelete a file overwritten in one pass. However, professional data recovery software may be able to find pieces of the files and recreate its contents. That's why we suggest that you use a sophisticated shredding algorithm like Peter Gutmann's algorithm that overwrites files in 35 passes. That way no recovery app will be able to restore the file in questions.
So, we've just answered the question "Can shredded files be recovered". Yes, they can if you use a one-pass algorithm and the person trying to undelete your file uses high-grade professional forensic software.
Don't confuse deleting a file with a shredder with hitting the Delete key or holding down Shift+Delete to bypass the Recycle Bin. When you simply delete a file, the only thing that gets removed is the file's entry. You don't see the file's name anywhere but the actual file is still on your disk and can be recovered until it's completely overwritten.
The problem is that you can't control when your computer will overwrite the files in question with new files. This is an advantage when you delete a file by accident and want to recover it, but it becomes a huge threat when your confidential files, like bank statements, tax returns, etc. can be recovered by anyone.
As mentioned above, digitally shredding a file will diligently overwrite all the data and thus make sure the file is truly erased. A file shredded in 35 passes can't be recovered even with advanced forensic software government agencies use.
That's a good question and only you know the answer because different people have different privacy concerns. The general recommendation is to shred only the files that contain sensitive information like your full name and address, bank account and credit card numbers, and the like. You may also choose to shred sensitive photos. In any case, there's no need to overdo it because file shredding usually takes time.
However, if you're planning to sell or donate your computer, it's a different story. Most people think that formatting a drive will do the trick, but that's not so. Even low-end free recovery programs can restore most of the data from a drive that's been formatted but they're useless if you use a disk wipe function, which is a part of Easy File Shredder. Instead of having to shred files one by one, the disk wipe will wipe everything off the disk using the algorithm of your choice. Only use this feature once you've copied everything you need from the drive because everything, including the operating system, will be gone.
Now you know that files deleting with a file shredder can't be recovered. Shredding a great way to protect your privacy and make sure no one gets hold of your deleted sensitive documents.