When a file is deleted from a computer, and the recycle bin is emptied, many would assume that the file is now gone forever. This is not at all the case.
When the file is deleted, it is flagged in the system as deleted. This hides the file from the user, but it can remain in the computers memory for years. This flagging process allows the computer to overwrite the file if it needs to, with new information, but this can often take some time.
If data recovery is carried out early on, it is very possible that the entire deleted file can be restored. If data recovery is attempted further down the line, the file may be recovered in whole, or in part - part recovery in this case could mean parts of an image would be missing, or that only part of a video would play.
Secure erasure of data is a constant issue with second hand hardware, particularly hard drives, but potentially any device using storage. Even non-persistent memory, that is designed to clear itself when a device is switched off, can be vulnerable - as studies have shown it is possible to recovery this with appropriate procedures.
Data erasure can be divided in to two techniques; software methods, and physical methods. Using software data erasure, new data in constantly written to the memory device, repeatedly overwriting the old data. The more passes that are carried out, and the more random the data being written, the more secure this method becomes.
Physical methods include degauzing, the process of physically removing traces of data using powerful magnets, and shredding, cutting the storage device into pieces. Shredding is seen as a fully secure method of data erasure, but clearly prevents reuse of the hardware.
Nick Johnston is an experienced computer security professional, with knowledge in computer programming and networking. He is self employed, working as a web developer, and Search Engine Optimisation (SEO) expert.
Nick also runs social networking website LiveFaceSpace, and an IT recruitment group.
Nick's other websites include The 2D Code, instructional website CSS Menu, and the home of polyphasic sleep.
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