What Is the Write Zero Method?

Details on the write zero data wipe method

Picture of a pencil erasing the word evidence

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Many file shredder and data destruction programs support the Write Zero software-based data sanitization method to overwrite existing data on a storage device like a hard drive.

The Write Zero data sanitization method may not stop the most advanced hardware-based recovery methods from extracting at least some of the deleted data, but it is likely to prevent all software based file recovery methods from lifting information from the drive.

The Write Zero method is sometimes, and more accurately, referred to as the Single Overwrite method. It may also be called zero fill erase or zero-fill.

What Does Write Zero Do?

Some data sanitization methods, such as Gutmann and DoD 5220.22-M, will write random characters over the existing information on the drive. However, the Write Zero data sanitization method is, unsurprisingly, usually implemented in the following way:

  • Pass 1: Writes a Zero

Some implementations of the Write Zero method may include a verification after the first pass, may write a character other than zero, or may write zeros over several passes, but those aren't common ways of doing it.

Most of the software programs that support Write Zero provide a way for you to customize the character and the number of times that verification takes place. That said, change those enough and you're not really using Write Zero anymore.

Is Write Zero Sufficient for Erasing Data?

Most likely, yes. However...

Some data sanitization methods replace your regular, readable data with random characters. As just mentioned above, Write Zero does the same thing but uses, well... zeros. In a practical sense, if you wipe a hard drive with zeros and then throw it away, your random dumpster diver who gets a hold of it won't be able to recover any of your deleted data.

If that's true, you may wonder, then, why other types of data wipe methods even exist. With all the data wipe methods available, what's the purpose of a zero-fill utility? The Random Data method, for example, writes random characters to the drive instead of zeros, so how is it that different than Write Zero or any of the others?

One aspect is not just what character is being written but how efficient the method is at overwriting the data. If only a single write pass is done, and the software doesn't verify that every piece of data has been erased, then the method isn't going to be as effective as methods that do.

In other words, if you use Write Zero on one drive and it verifies that all the data has been overwritten, then you can be confident that the information is less likely to be recovered than if the same data were overwritten with the Random Data method but didn't verify that each sector was replaced with random characters.

However, certain characters might also provide better privacy than others. If a file recovery program knows that the data was overwritten with zeros only, it makes it significantly easier to sift through what data exists than if the program doesn't know the characters used, like those in the Schneier method.

Another reason for all the other data wipe methods is that some organizations want to prove that their information is being erased in a specific manner that's most likely to prevent recovery, so they use a certain data sanitization method with certain parameters for all their data wipe needs.

Programs That Support Write Zero

In Windows 10, Windows 8, Windows 7, and Windows Vista, the trusty format command, by default, uses the Write Zero sanitization method during the format process. You can utilize that command in a command prompt to write zeros to a hard drive without having to download any extra software or special tool.

See How to Use the Format Command to Write Zeros to a Hard Drive for details on this. It's not quite as simple as it sounds when you're trying to do this on your main system drive.

There are also 3rd party programs that support using the Write Zero method for erasing data, such as DBAN, HDShredder, KillDisk, and Macrorit Data Wiper. Some of these programs can be used to erase the hard drive you're actively using (like the C drive) by running from a disc or flash drive, and others run within the operating system to erase other drives, like removable ones.

Other tools use the Write Zero method for deleting specific files instead of everything like the programs above do. A few examples of tools like that include WipeFile and BitKiller.

Most data destruction programs support multiple data sanitization methods in addition to Write Zero, so you can most likely pick a different method, if interested, once you've opened the program.

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