An eraser program is a piece of software which is designed to remove data from a hard drive. Data erasure goes beyond deletion, actually destroying the data so that it cannot be retrieved. Erasers, as they are known, can be used to prepare a computer for transfer between two individuals, to remove sensitive data from a computer so that it cannot be accessed, or to prepare a computer for recycling. Numerous free data eraser programs are available online from reputable sources, and it is also possible to buy eraser programs.
When someone deletes a file by hitting “delete” or dragging it to the trashcan/recycle bin, the computer removes the pointers to the file, but the data is still there. It's possible to restore the data using a data restoration program, and the process is not very difficult; even a novice can restore deleted data with the right program. This is a concern for people who handle sensitive data and for people who want to pass on or get rid of their computers without having to worry about someone resurrecting personal data.
When an eraser program is run, the program overwrites the hard drive with meaningless data, writing over the traces of previously deleted information to scrub the hard drive clean. Eraser programs can perform as many as seven passes of the hard drive to eliminate all of the information stored on the drive, rendering the computer totally usable, but absent of any personal data.
The ability to scrub a hard drive with an eraser program rather than having to destroy it to remove data is important. Hard drive wipes can also be accomplished through physical destruction of the drive, or be degaussing it, but these techniques also destroy the drive. With an eraser program, someone can give or sell a computer to someone else, donate a computer to a charitable cause, or send a computer for recycling in confidence that the data on the computer has been successfully removed.
Data erasers can also be used for applications like truly erasing Internet history, and they are sometimes used by criminals to cover up their tracks. Increasing knowledge among police forces about technology and the development of computer forensics as a specialty has forced criminals to get more creative about handling their sensitive and potentially implicating data. Smart criminals will run an eraser program on a computer used for questionable activity to reduce the risk of being caught and to make themselves harder to prosecute.