SpyZooka provides a range of overwrite options in its Drive Shredder, File Shredder, and Scan features.

An overwrite, in the context of shredding algorithms, refers to the number of times the data on your hard drive is written over.

The overwrite algorithm can be as simple as a single overwrite of zeroes, or it can involve a combination of zeroes and ones, random data, or a complex mix of different overwrites.

You can think of it like repeatedly typing zeroes until your previous data on the hard drive is concealed.

A single overwrite represents applying the chosen algorithm once. For example, if the algorithm involves writing all zeroes, it will overwrite your data once. If it's a 3-overwrite algorithm, it will apply three layers of overwrites to your data.

Typically, fewer overwrites offer faster completion but may be less secure. More overwrites provide enhanced security but can take longer to complete.

When you delete a file from your computer, it is not completely erased. While it may not be visible on your computer, it can potentially be recovered using file recovery tools.

If you plan to sell or give away your computer, it is crucial to use a drive shredder to overwrite all your data to ensure that it cannot be recovered by another person. Without proper shredding, your files, pictures, and browsing history remain recoverable.
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3 Overwrites > the overwrite option we recommend. Its the fastest option and very secure. Its unlikely anyone would need more overwrites as even the US Department of Defense uses 3 overwrites for their standard shredding algorithm.

7 Overwrites > More secure but slower.

35 Overwrites > Like bringing a fire department hose to a water balloon fight, its perhaps a bit more than you need.

SpyZooka uses it's own proprietary overwrite algorithm. It writes a random byte for each overwrite. The 3 overwrite option writes 3 random bytes over your data, 7 overwrites writes 7 random bytes and 35 overwrites writes 35 random bytes over your data.

Other overwrite algorithms, some of which are open source, are listed below.
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Simple Deletion > 0 Overwrites > this is the standard used on Windows. Its fast and simple for making files difficult to recover. This happens when you add a file to the recycle bin and delete it. Any file over 32kb will leave data on the hard drive that can be recoverable.

Pseudorandom Data > 1 Overwrite > A fast shredding option that writes random data of the existing data. 

British HMG IS5 > 1 Overwrite > A fast shredding algorithm that overwrites the data one time. It serves as the base for the same algorithm with 3 overwrites.

Russian GOST P50739-95 > 2 Overwrites > A Russian developed shredding algorithm using two overwrites of your data. The first overwrite uses zeroes over all your data with the second overwrite using random data.

US Army AR380-19 > 3 Overwrites > A 3 overwrite algorithm developed by the US Army for shredding digital media.
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US Air Force 5020 > 3 Overwrites > A 3 overwrite algorithm developed by the US Air Force for shredding digital media

British HMG IS5 > 3 Overwrites > This 3 overwrite method is more secure than the 1 overwrite algorithm.

US DoD 5220.22-M (8-306./E) > 3 Overwrites > This 3 overwrite algorithm is specified by the United States Department of Defense for securely shredding their digital files.

German VSITR > 7 Overwrites > Originally developed for Germany's Federal Office for Information Security, it has since been discontinued for government use.

US DoD 5220.22-M > 7 Overwrites > The United States Department of Defense shredding algorithm for digital media. 

Schneier > 7 Overwrites > Designed by Bruce Schneier and explained in his book Applied Cryptography: Protocols, Algorithms, and Source Code in C. 

Gutmann > 35 Overwrites > Designed in 1996 to securely shred all the data on your hard drive. Uses 35 different overwrites patterns for your hard drive, some of which are outdated for modern hard drives.

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