A lot of people are worried about privacy in today’s computing world, as they rightly should be. One of the ways to ensure privacy is to erase files ‘securely’. There are many software tools that help do this activity. For many of the tools, their claim to fame or in this case claim to ‘more security’ is the number of times a file is overwritten.
This is pure FUD – Fear, Uncertainty and Doubt (http://en.wikipedia.org/wiki/Fear%2C_uncertainty_and_doubt and http://en.wikipedia.org/wiki/Fud).
To have a file securely deleted, it is enough to overwrite it once, before deleting it. Yes. You read it correctly. ONCE is ENOUGH.
The procedure for secure deletion is very simple. Have a program that overwrites the selected file using an ’1' character or any other character of your choice. Once that is done, delete the file. Now, there is not chance that the file can be recreated, even after recovery.
Not convinced? Visualize this situation. You have a text document that contains your banking information – user names and passwords.Now suppose the size of this file was 500 Kilobytes. Using the secure erase method described above, simply overwrite the text files with the ’1' character. Before deleting the file, try to open it and verify if you can recover your banking information. On opening the file, you will find a text file filled with 500 Kilobytes worth of ’1”s – the file will contain nothing but ’1's. Go ahead and delete the file. Now use deleted file recovery software to ‘undelete’ the file. After recovery, open the file and see what you get back – a file full of ’1”s or your bank user names and passwords.
While I described this method for a text file, it will also work for files like .doc, .xls, .pptx, .psd, to name a few. The downside of overwriting such files is that if you try and open them using Word or Excel or Powerpoint or Adobe Photoshop, these programs will not be able to do so, as the file formats no longer match their expectation. For verification, you can drop these files into Notepad and it will happily display your data – loads of ’1's. Now go ahead and delete the file with no worries.
Still not convinced? build an application using the code I will post in the entry that will follow and try it for yourself.
Sometimes, simple solutions beat the totally overblown claims of many comparative products.