I wrote an article last year called Computer Forensics 101, which described the virtual impossibility (outside of physically destroying the hard drive) of truly deleting a file from your computer. With that in mind, you still need to “sanitize” an old computer before selling or giving it away. In order to enhance security and your own peace of mind, you may also wish to sanitize the computer that you currently use. If you have no idea what I’m talking about, visit my website and read the above-mentioned article.
Typical file deletion procedures involve “deleting” the file and emptying the “recycle bin.” These procedures are akin to taking a book and using a permanent marker to black out a chapter name in the table of contents. The chapter is still in the book, but you wouldn’t know that from reading the table of contents. When you delete a computer file, its name is simply removed from the table of contents. However, unless overwritten by other data, the file still resides on the hard drive.
My latest research project has been to examine so-called file “shredding” programs. These programs purport to erase “deleted” files by physically overwriting the hard drive space that they occupy with a random series of the digits zero and one (0 and 1). Because hard drives are a magnetic media built of rust and rocks (metal oxides and magnets), shredding programs will overwrite deleted files numerous times in order to ensure that the file’s magnetic bits become completely scrambled.
While it may still be possible to reassemble these “truly” deleted files, it would take someone with the super-computing ability and financial resources of the National Security Agency to pull it off. Our greatest present concern is protecting our hard drives from dumpster divers, thrift store shoppers and criminal computer hackers; this we can do.
There are many free and for-pay file erasing/shredding programs advertised on the Internet, with lots of phony “review” websites that give high marks to every program that exists. After much study and consideration, I paid $25 for Clean Disk Security, a simple but very effective program available at www.theabsolute.net/sware/clndisk.html.
There are some things that must be done in order to have a trouble-free file-shredding experience. At the minimum, they are: (1) disconnect from the Internet, (2) “delete” your files and empty the Recycle Bin, (3) run the CCleaner program and delete all cookie/history files, (4) defragment the hard drive, (5) close all programs that are running in the background. Go to Control PanelAdministrative ToolsServices, and right-click to stop as many Services as possible. Press ControlAltDelete, go to Task ManagerProcesses, and stop as many processes as possible, (6) in Clean Disk SecurityConfig, check “clean swap file, erase traces” and uncheck “maintain a log,” (7) check “clean everything” (uncheck “plugins”) and choose a “method.” Three passes should be fine, “NIS-7” will be very secure and very slow, “Gutmann” will be extremely secure and excruciatingly slow, (8) defragment the hard drive again. As Hillary Clinton may have once said, “Happy shredding!”