How to safely delete data and the software used

Because of the need to completely delete some of the data, remember that some storage devices with such an option: Replication n times to completely erase the traces of the original information, but Windows have any good tools to do this job? Search the Internet, find a lot of "file Grinder" "Super File Grinder", software and miscellaneous, let a person at a loss.

Downloaded several, such as 360safe production of 360 file grinder, green software, but only to support the deletion of files, can not clear the entire folder, it is inconvenient to use, and does not support the free space on the disk to clean up. In addition, there is no help file to explain the principle of its safe deletion. Abandon it. Other software such as bps Data Shredder, File Pulverizer, etc. are not free.

After careful analysis and trial, finally found a better: by Finnish students Sami Tolvanen (Personal Web page: http://www.tolvanen.com/sami/) written eraser, the current version 5.8. ZDNet has a Chinese version of the download (http://down.zdnet.com.cn/detail/5/45730.shtml) Although the Chinese to do a very rough, but the function to meet the requirements. Because it often takes a long time to safely delete data, the software's planning task function is very practical.

The principle of data security deletion

Note: The following is a reference to the "How to remove data from a hard drive", as shown in the Note References section [1].

"Deleting files does not actually delete data when it involves data that is stored on the computer. Information about the file exists in a directory so the operating system can easily find it. When you delete a file, all you do is remove it from the directory and mark the hard drive area where it is stored to store the new data. Until the area is overwritten with new data, you can restore the deleted files, which is how to recover the lost data. It is also the working principle of the file recovery software, which restores files that you have not seen from the file directory.

There is only one way to completely delete data: that is to overwrite the data on your hard drive. You can reformat (note: You must do low-level formatting), or you can use data cleansing software to rewrite the hard disk with random data.

Two main methods of overwriting data

Gutman method

It is based on Peter Gutman's paper: "Safely remove data from magnetic and solid-state storage" [2]. This approach provides the highest level of security, and data is overwritten 35 times with carefully selected data, so that the overwritten data is never recoverable again, and the disadvantage is that it takes too long.

US Department of Defense 5220-22. M method

It is based on the 5220-22 recommended by the U.S. Department of Defense. M method, this method will cover the data 7 times, not as safe as the Gutman method, but faster than the Gutman method. ”

PS, Eraser 5.8 also provides a method of covering 1 times with pseudo random numbers, which is fast enough to deal with general data recovery software, but with a low degree of security, I think there is a way for professional agencies such as national security agencies to recover.

Also PS, Apple's Mac OS has its own security removal feature, and Ubuntu has command line tools shred