On many computers, the operating system and user data is stored inside a component called the hard drive. You may remember my contribution to Tech Tails #946 in which I went into some detail on the inner workings of hard drives. This week, I will cover some different methods of deleting and recovering files from hard drives.
Data is stored on hard drives in the form of magnetic signals of varying intensity. A weak magnetic charge can be interpreted by the computer as a “0”, and a strong charge as a “1”. With enough of these simple signals, a computer can store a song, a video, or just about any type of information imaginable.
When a user deletes a file from a computer the standard way, by moving it to the trash and emptying the trash, it does not actually remove the magnetic signals from the hard drive. Parts of the file are altered in a way that instructs the computer to ignore it and treat it as blank space. The actual data of the file is not erased until it is overwritten with a new file. This is done because it is much faster than actually erasing the data every time a file is deleted from the computer.
In versions of OS X previous to 10.11, a “Secure Empty Trash” option existed. This would overwrite all of the data in the trash with empty data. This feature was removed in OS X 10.11, because Apple could not guarantee that the user of the computer had not made other copies of the file on the same computer, which would not be erased. Apple recommends enabling Filevault if you are concerned about the security of the data on your computer. You can learn more about Filevault in my contribution to Tech Tails #942.
Be cautioned: If you enable Filevault and then forget the password to your computer, your data will be permanently unrecoverable.