After you delete a “sensitive” file, do you rest assured that nobody will ever be able to access that file? Well, think again… because you are not completely safe until you really remove that file!
What happens is that when you delete a file, this operation is translated as:
* mark the disk space occupied by that file as available, so that other files can use it;
* mark the file as gone from the directory it was in, so it won’t be listed anymore;
* leave the actual contents of the file on the disk, so it can be recovered;
…and this is happening in many operating systems, like Windows XP (NTFS), Mac OS X (HFS Plus) or GNU/Linux (with a kernel version greater than 2.4).
The last operation is the one causing problems in some cases, although it has its benefits. But it’s not that bad, because, along with new bytes getting written to the disk, that disk space marked as available will be used by other files eventually. So, the content of the deleted file is replaced, making it unrecoverable by software means (I’ve specified software means, because on older hard disks it’s possible to recover a deleted file through physical means and with the right equipment, even if new information has been written on that disk).
If you don’t want to wait for that, there are some alternatives:
1. File shredding (preferably on the whole partition rather than individual files – disk free space wiping);
2. store the file using strong encryption at all times, in which case there won’t be any useful data to recover (if the encryption key is secure enough);
3. destroy the media (incinerate, use acid, degauss the platters);
These last two are very effective alternatives to protect data privacy, though they are much more that an average user needs. And since using file shredder software is sufficient enough to ensure that the data can’t be recovered, I think that’s the best alternative to use.
File shredding (also called file wiping) signifies secure deletion of a computer file, so that it can not be restored by any means, and it can be done using specialized software – usually called File Shredder.
Tip: Although your computer is telling you that there is a certain amount of free space on your disk, it doesn’t necessarily mean that and it’s always a good thing to do a free disk space wipe – some people say that it’s even better to do it three times in a row!
Tip 2: Before you decide to buy such software, search the Internet for reviews on the most popular file shredders.