REMEMBER YOU CAN NEVER EVER DELETE YOUR FILES. MEMORY CAN BE CREATED BUT NEVER BE DESTROYED!!!

Delete has been common word which is used by every individual at least once in a day. We delete our chats, videos, messages, photos, etc. everyday but HAVE YOU ever thought WHERE DO THESE DELETED DATA GO? According to the Meriam Webster, Delete means to remove (something, such as words, pictures, or computer files) from a document, recording, computer, etc. Delete has been derived from the latin Word ‘deletus’. The GOOGLE NGRAM VIEWER allows you to search words and phrases in 5.2 million’s book published between 1500 and 2008. It’s a great way to see how the words we use have changes overtime. 1979 was a significant year. According to the Ngram Viewer, it was the first year we begin to use the word delete more often than the word erase. People have been using this word from time to time. Although it has become popular only after the advent of computers.

HOW DOES A COMPUTER FORGET??

Moving a file into the trash (Recycle bin) is just the beginning. To protect an accidental deletion, the file that we delete from our system remains in recycle bin where it needs an ultimate resurrection i.e full removal of file from system. When we open the trash we can see the deleted file in the trash and we restore that file if we wish. But when we delete the file from the recycle bin where does it go? Have you ever seen your file moving out of your system? What goes in must come out. Have you ever thought about that?

 

Remember, when you delete a file from the recycle bin it’s actually not deleted from the system, it is marked as deleted or empty. Available if and when new data needs to be stored somewhere. The file’s home has become available real estate but the file itself hasn’t moved out. Only the pointers (pointer holds the address of a particular data) have gone away. Pointers are another type of data on your device that point to places in memory where the actual file they are referencing can be found. They are a bit like table of contents, which means that on most operating systems deleting the file or emptying the recycle bin is like deleting a chapter from a book by turning to the table of contents and marking the chapter as empty but actually when you turn pages you can find the chapter which had been marked as empty in the table of contents. To a computer reading table of contents it looks like the space is empty but of course that doesn’t change the fact that the contents of the chapter are still there.

On any hard disk, there is a table stored that says "File-X is stored in the following location(s): ", let’s say File- X is located in location- A.

When the user access the request to File-X, the drive knows where to go look for it. When a user request for the deletion of File-X, location- A is marked as empty inside the file table. Therefore File- X stays there but to the user location- A is nothing but reusable  empty space which means that space is available for new data.

As long as no new data had been written over the sectors that originally housed that information, everything was still there and you could recover it simply by telling the table to restore the data using some special softwares like Recuva which fetch the data from the location(s) which are marked as empty, they can even find  a file and save it , bring it back mark it not available, undeleted. Over writing the new data over the sectors that originally housed that information is also not enough because of something called bad sectors. Bad sectors are the area on the hard drive which cannot be over written because of failed transistor or physical damage. That’s means that any data that was ever put there, stays there.

So that allows a pretty easy method of recovering a file providing the sectors that housed it hadn't yet been overwritten. The Windows recycle bin simply delays this process by moving "deleted" files into a special holding area, noting the original location and date it was deleted. After a certain period of time, the "proper" delete takes place.

Now, some people realised that if they wanted to actually get rid of a file, a simple delete might not be sufficient, after all simply by restoring the data in the file table, there's a reasonable chance it might be able to be recovered, especially if it hadn't been a long time since the delete took place. So a method called "zero filling" was invented. This involved filling every byte of the original file with a "0", and then deleting the file. That way, even if you do restore the data in the file table, all you're going to get back is an empty file. It effectively ensures that the disk sectors are already overwritten at the time of deletion.

Fool proof? Not quite. To understand the next bit requires some knowledge of how magnetic media operate. The surface of the drive is covered in a magnetically influenceable material which is divided up into small chunks. Each of these chunks can represent a binary 0 or 1 depending on the magnetic orientation. Let's say that a horizontal orientation represents a zero and a vertical orientation a one. The drive reads the orientation of each tiny segment and returns a 0 or a 1. So far so good. 

So here's an example chunk of drive representing part of a file:

So now we want to completely erase this file by changing everything to zeros. So we tell the drive to change everything to an horizontal orientation. Simple, right?

Except that the magnetic write head doesn't do this with 100% efficiency. That is, the orientations are never 100% horizontal, or 100% vertical. The read head will quite happily read a bit that is 98% vertical as a 1, or just off horizontal as a 0. It doesn't really matter, as long as you can make out what it's supposed to be.

So there, everything will now be read as a zero. But by looking at the precise orientations, you can tell what used to be a 1 and what used to be a zero. If you've got access to the exact values of orientation, you can tell what the sectors used to be.

That's the principle of the hard core recovery available to the FBI and other agencies (even you, if you've got enough money). It is impossible to delete the data!!! So if you are in the United States Department of Defenses and you don’t want to take any risks, you will also shred(break), physically polarize unwanted drives. The US, Europe, Japan often sends such electronics waste to dumps in Ghana, like this one.

 

This city in Ghana is known as “Earth’s digital dumping ground”. Why Ghana? Well, it is cheaper to send unsalvageable electronics to Africa, marked as a donation, than it is to properly recycle them. But there in this electronics dump files can be still brought back to life. Organized criminals in Ghana have managed to successfully recover data from unregulated e-dumps. They have been able to find confidential multi-million-dollar agreements, involving the Defense Intelligence Agency, Homeland Security and the TSA. If you want to delete something ,destroy it, erase it the ultimate thing you have to do is just burn it!!!

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