An overwrite in a shredding algorithm is the number of writes over your hard drive data.
An overwrite algorithm can be as simple as a single overwrite of zeroes across your data, or writing zeroes and then 1's, writing something completely random, or as complicated as a mix of different overwrites.
Think of it like typing a 0, over and over again until it hides your data previously on your hard drive.
One overwrite is simply one overwrite of that algorithm. So if the overwrite algorithm is all zeroes, it writes zeroes over your data one time. If its a 3 overwrite algorithm it writes 3 layers over your data.
Typically fewer overwrites are less secure but finish faster. More overwrites are more secure but can take much longer.
When you delete a file from your computer is is not truly deleted. It is not displayed on your computer, but it can be recovered using file recovery tools.
If you ever give away or sell your computer it's important to use a drive shredder to overwrite all your data so it cannot be recovered by another person. All your files, pictures and history is recoverable unless you shred it.
ZookaWare' 3 Overwrite options for Drive Shredder, File Shredder and Scan:
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 nuclear bomb to a knife fight, its perhaps a bit more than you need. But sometimes more than what you need is simply fun!
ZookaWare 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.
Common Deletion and Overwrite Options
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.
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.
Do you have any questions or feedback about overwrites and ZookaWare? Let us know in the chat widget to the right! We are here daily to answer all your questions about overwrites!