Does a computer file truly get "deleted"?

They are still there on a hard disk. They don’t go away unless their memory location is written over multiple times. Alternating zero and one replaces is the only way to truly “delete” a file.

Yeah, they don’t really ‘go away’ most of the time. What you do when you ‘delete’ or ‘recycle’ the file is basically telling the computer that that space is now available again, that’s all. All the bits are still there until they’re overwritten, which may be a while depending on what the system is used for, which is why specialized programs can go in and retrieve ‘deleted’ files.

Now, from the physical perspective of ‘nothing ever gets “completely destroyed”’, that’s not 100% true. Information is lost over time, that’s part of the second law of thermodynamics (order is lost to disorder, information is ordered). So, over time, the information will be lost. So destruction of data to random overwrites, as happens when you do a real data cleansing on a hard drive, does actually destroy the data. But that is not normally what happens.

It depends.

Using the normal methods like dropping it in the Recycle bin or the del command pretty much just delete the file system markers saying that there is a file in a certain section of the drive, but leaves the file itself there until it gets overwritten by other data.

Using other methods such as the Guttman method (overwriting that section of the drive 35 times with random 1’s and 0’s), the file is, for all practical purpose, obliterated. And as it only ever truly existed as a pattern of magnetic anomalies, there is no physical evidence of it ever having existed. In fact, even without it being deleted, there really isn’t much physical proof that it exists; such as the nature of information. It’s intangible!

Great question. I just recently noticed that my system care provides shredding and it says that that is better than deleting. So if I shred than does that mean that the file is gone for good? It says it replaces the file with zeros.

Nothing physical is stored on the hard disk drive, so nothing is created or destroyed and no laws of physics are broken. The bits, the binary 1s and 0s which represent the files you use, are determined by the direction of the magnetization on the disk, thus the disk is analogous to lots and lots of densely packed switches, and those switches are either in a 1 or a 0 position.

Unless you’re using a solid state drive…

Funny how when you get a virus it has no problem destroying stuff beyond repair.

I am not sure how these new computer operating systems work, but in the Windows 3.1 era, if you deleted a program or file, it just deleted the first character of the name of that file. DOOM.PGM would become ~OOM.PGM. The rest of the file would still be there, until another program or file wrote over the disk space used by that file.

The information stored in your computer is not a physical thing. It’s just patterns, like writing on a page. If you somehow gathered all the ink forming that writing into a blot in the middle of the page, nothing physical would be lost- but the message would be gone.

Your computer maintains a data structure called the “file system”, which is how it keeps track of where the data is stored and how to retrieve it. Bulk storage (“block”) devices are divided up into logical sections, each with an assigned “index node” (inode). The inodes are used to keep track of the data. When you delete a file, the inodes relevant to the data contained in the file are overwritten, but the data is still present in the device. At this stage, “undelete” tools can reconstruct the inode database and find the pieces of the file. The longer you wait (as in, the more read / write activity takes place on the device in the meantime) the harder it is to reconstruct such files. Eventually the data as well as the inodes will have been overwritten, and the data will not be retrievable except by some pretty hard-core forensic analysis (one of the guys in my nonprofit org does this stuff. It’s pretty interesting.)
Alternatively, as @jerv points out, you can deliberately scramble the data before overwriting the inodes, and the data will then become unreadable.

So, the short answer is: a deleted file becomes noise.

Here is an interesting video on just this subject.

@Pandora Your observation is pretty cool, really. A truly effective delete tool would be a directed (user-directed) virus.

No. Only their entry in the file table is removed. The actual data is still there and only gets lost once it is overwritten with new data.

The recycle icon captures the idea. You are not destroying the bits in the file. You are just releasing them so they can be reused for other files.

You can hold a very strong magnet over the disk. This is what we do at our company before donating old PCs.

This may be different with some of the more recent technology, but even “obliterating” files with special software isn’t as effective as the suggestion by @mattbrowne . Having also worked at computer companies, powerful magnets tend to do the best at destroying data on a disk (short of incinerating the hardware).

NASA and some other big tech enterprises have technology that can pull data from hard disks no matter how a user has tried to destroy it. My dad worked at Enron and I remember all their computers were shipped there for this purpose after the scandal. (Except the one I have in my closet) Sure it costs 10–20 thousand bucks a pop but hey some data is worth it.

So really you have two options to REALLY get rid of it. Magnets or Fire. Gotta love nature!

@gambitking The average user doesn’t have anything sensitive or valuable enough to justify the cost of certain data recovery methods though. It’s all about how much the data is worth.

@gambitking “Kill it! Kill it with magnets!!”

@Blueroses Only if you set the magnets on fire first.

@jery , oh I know there’s scarcely a need to actually go that far, I’m just playing the devil’s extremist.

MAGNABURN ALL TEH THINGS

If you don’t set them on fire, you’re not being extreme ;)

Amateurs.

Magnets + fire = plasma.

PLASMA CUTTER FTW!

Better yet, turn the device itself into an energetic plasma. You may need a small star for this :)

Try reading it after that!

Relevant

@jerv Ninj’ad