Overwriting a file

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Overwriting a file

For example, before a hard drive is re-used within an organization, its contents may be cleared to prevent their accidental disclosure to the next user. Purging[ edit ] Purging or sanitizing is the removal of sensitive data from a system or storage device with the intent that the data cannot be reconstructed by any known technique.

Destruction[ edit ] The storage media is made unusable for conventional equipment. Effectiveness of destroying the media varies by medium and method.

Conversely, destruction using appropriate techniques is the most secure method of preventing retrieval. Overwriting[ edit ] A common method used to counter data remanence is to overwrite the storage media with new data. This is often called wiping or shredding a file or disk, by analogy to common methods of destroying print mediaalthough the mechanism bears no similarity to these.

Because such a method can often be implemented in software alone, and may be able to selectively target only part of the media, it is a popular, low-cost option for some applications. Overwriting is generally an acceptable method of clearing, as long as the media is writable and not damaged.

overwriting a file

The simplest overwrite technique writes the same data everywhere—often just a pattern of all zeros. At a minimum, this will prevent the data from being retrieved simply by reading from the media again using standard system functions.

In an attempt to counter more advanced data recovery techniques, specific overwrite patterns and multiple passes have often been prescribed. These may be generic patterns intended to eradicate any trace signatures, for example, the seven-pass pattern: One challenge with an overwrite is that some areas of the disk may be inaccessibledue to media degradation or other errors.

Software overwrite may also be problematic in high-security environments which require stronger controls on data commingling than can be provided by the software in use. The use of advanced storage technologies may also make file-based overwrite ineffective see the discussion below under Complications.

There are specialized machines and software that are capable of doing overwriting. The software can sometimes be a standalone operating system specifically designed for data destruction. There are also machines specifically designed to wipe hard drives to the department of defense specifications DOD He suggested magnetic force microscopy may be able to recover such data, and developed specific patterns, for specific drive technologies, designed to counter such.

Daniel Feenberg, an economist at the private National Bureau of Economic Researchclaims that the chances of overwritten data being recovered from a modern hard drive amount to "urban legend".

Erased information in the gap has not been recovered, and Feenberg claims doing so would be an easy task compared to recovery of a modern high density digital signal.

Only degaussing or physical destruction is acceptable for the latter.

overwriting a file

They point out that the long time required for multiple wipes "has created a situation where many organisations ignore the issue all together — resulting in data leaks and loss. Applied to magnetic mediadegaussing may purge an entire media element quickly and effectively.

Degaussing often renders hard disks inoperable, as it erases low-level formatting that is only done at the factory during manufacturing. In some cases, it is possible to return the drive to a functional state by having it serviced at the manufacturer.

However, some modern degaussers use such a strong magnetic pulse that the motor that spins the platters may be destroyed in the degaussing process, and servicing may not be cost-effective. Degaussed computer tape such as DLT can generally be reformatted and reused with standard consumer hardware.

In some high-security environments, one may be required to use a degausser that has been approved for the task. If the decryption key is strong and carefully controlled, it may effectively make any data on the media unrecoverable.

Even if the key is stored on the media, it may prove easier or quicker to overwrite just the key, vs the entire disk. This process is called crypto-shredding.

Encryption may be done on a file-by-file basis, or on the whole disk. Cold boot attacks are one of the few possible methods for subverting a full-disk encryption method, as there is no possibility of storing the plain text key in an unencrypted section of the medium.


See the section Complications: Data in RAM for further discussion. Other side-channel attacks such as keyloggersacquisition of a written note containing the decryption key, or rubber-hose cryptanalysis may offer a greater chance to success, but do not rely on weaknesses in the cryptographic method employed.

As such, their relevance for this article is minor. Media destruction[ edit ] The pieces of a physically destroyed hard disk drive. Thorough destruction of the underlying storage media is the most certain way to counter data remanence.

However, the process is generally time-consuming, cumbersome, and may require extremely thorough methods, as even a small fragment of the media may contain large amounts of data.

Specific destruction techniques include: Physically breaking the media apart e.Apr 20,  · Hi All, I have this VBscript that needs to copy a surtain file from one directory to another one. When it is copied I dont want it to have the name of the original file but it needs to overwrite a file .

I have a macro that saves a file using the following code. If a file already exists with the same name, Windows asks if I want to replace the original file.

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Selecting Yes, overwrites the file and. When you a delete a file, it isn’t really erased – it continues existing on your hard drive, even after you empty it from the Recycle Bin. This allows you (and other people) to recover files you’ve deleted. Data erasure (sometimes referred to as data clearing or data wiping) is a software-based method of overwriting the data that aims to completely destroy all electronic data residing on a hard disk drive or other digital media by using zeros and ones to overwrite data onto all sectors of the device.

By overwriting the data on the storage device, the data is rendered unrecoverable and achieves. I have a macro that saves a file using the following code.

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If a file already exists with the same name, Windows asks if I want to replace the original file. Selecting Yes, overwrites the file . Eraser is an advanced security tool for Windows which allows you to completely remove sensitive data from your hard drive by overwriting it several .

Data erasure - Wikipedia