We’ve all heard the stories about people buying computers off of eBay or Craigslist and then being able to recover personal information from the disks on those computers. Before I delve into why this is possible, let me point out that the vast majority of computers out there are running on Windows. According to NetApplications, Windows commands 91.31% of the market with Mac OS at 3.95% and Linux weighing in at less than 1%.I point this out because I’m going to focus on this issue from a Windows perspective.
I won’t get too geeky here, but basically, the filesystems used by Microsoft uses a table that contains information about the files that reside on the physical disk. This table contains the filename, physical location on the disk and other pertinent information. When you delete a file, the file is deleted from the table, but the actual file on the hard-disk is never touched. This approach isn’t all bad, in fact, what you get out of this is speed and performance. If the operating system took the time to fully destroy every file you delete, you might get very frustrated, because the process takes time and depending on the size of the files being deleted, it can take a mighty long time.
Before we move on, let me just say, don’t fall into the trap of thinking that just because you empty your recycle-bin that you’ve taken care of the problem, because you haven’t. Perhaps I’ll write an article on the recycle-bin someday, but suffice it to say that all it does is make it easier to restore deleted files. When you delete its contents, you are doing nothing to eradicate it from your hard-disk.
Ok, let me setup a scenario for you. You know that it’s possible to recover data from your hard-drive but you want to sell an old PC because you’ve just bought a new one, what do you do? Another scenario is you’re leaving your job and you want to delete all your personal files so that they can’t be recovered, what do you do?
The answer – install a file shredder. There are a number of tools out there that’ll do this, but as always, I look for the open source solutions first and there’s a fine option available for the Windows platform that does exactly what we’re looking for and it’s appropriately named Eraser. For those of you running on a pre-Vista windows OS, just go to the download section of the Eraser web-site and you’ll find what you’re looking for. If you’re running Vista, you can download Eraser 5.8.3 which is Beta software, but it should work for you.