How-to Booklet

6. How to destroy sensitive information

Submitted by admin on Thu, 11/20/2008 - 13:01

The previous chapters have discussed a number of tools and habits that can help you protect your sensitive data, but what happens when you decide that you no longer need to keep a piece of information? If you determine, for example, that your encrypted backup copies of a particular file are sufficient, and you want to delete the master, what is the best way to do so? Unfortunately, the answer is more complicated than you might think. When you delete a file, even after you empty the Recycle bin, the contents of that file remain on your hard drive and can be recovered by anyone who has the right tools and a little luck.

In order to ensure that deleted information does not end up in the wrong hands, you will have to rely on special software that removes data securely and permanently. Eraser is one such tool, and is discussed below. Using Eraser is a bit like shredding a paper document rather than simply tossing it into a bin and hoping that nobody finds it. And, of course, deleting files is only one example of a situation in which you might need to destroy sensitive data. If you consider the details that someone, particularly a powerful, politically-motivated adversary, could learn about you or your organisation by reading certain files that you thought you had deleted, you will probably think of a few more examples of data that you'd like to permanently erase, by destroying outdated backups, wiping old hard drives before giving them away, deleting old user accounts, and clearing your web browsing history, for example. CCleaner, the other tool described in this chapter, can help you face the challenge of deleting the many temporary files that your operating system and applications create every time you use them.

Background scenario

Elena is an environmentalist in a Russian-speaking country, where she maintains an increasingly-popular website that highlights the extent of illegal deforestation in the region. She has created a backup of the information used to create the website, and she keeps copies of it at home, in the office and on her new laptop. Recently, she has also begun to store a copy of the webserver's visitor logs and the database containing her users' forum posts. Elena will soon be travelling internationally, to attend a large global conference of environmental activists, some of whom have reported having their laptops taken away for over an hour at border-crossings. To protect her sensitive information, and the safety of her more political forum participants, she has moved her home and office backups onto a TrueCrypt volume and removed the copy from her laptop. She asked her nephew Nikolai for advice, and he has warned her that she needs to do more than just delete her old backup if she is worried about having her computer seized by border officials.

What you can learn from this chapter

  • How to remove sensitive information from your computer permanently
  • How to remove information stored on removable storage devices like CDs and USB memory sticks
  • How to prevent someone from learning what documents you have previously been viewing on your computer
  • How to maintain your computer so that deleted files cannot be recovered in the future
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