The Molecular Universe

Information on your hard drive can be read long after you have deleted a file or scrapped your computer. Find out how to protect your information and avoid many problems, such as identity theft, that can result from the inappropriate use of your information.

Your computer's hard drive is an amazing device. It uses magnetism to store electronic data. The principle that it operates by is similar to the children's science experiment where a needle is magnetized through being stroked by a magnet in order to make a compass. Your computer's hard drive uses the same physical phenomenon on a minute scale to store gigabytes of data on the surface of a magnetic disk. First the hard drive magnetizes regions of the hard disk, then a sensitive probe is used to read the same regions by detecting the magnetism on the disk. When you turn the power off to the computer the data is still stored on the disk, and there it will remain for many years. Every time you save a document, your computer saves information on your hard disk. Every time that a program that you are using, like a web browser such as Internet Explorer, Firefox, or Safari, needs to save information permanently, it will save the information on your hard disk.

So far, you might think, this is fine. When I am finished with my documents, I will simply delete them and the information will be gone forever. However, you need to know the following. Generally speaking when you delete a document, all that happens is the reference to that document is removed from the list of items which are stored on the hard drive. The information in the document is still on the hard drive. Why so, you might ask? Well programmers are forever taking short cuts and it is very much faster to remove the reference to a document than to find the information on the disk and remove the actual bits and bytes for the document. It is as though you were asked to remove a book from the library. Instead of actually removing it, you simply delete it from the catalog. No one will ever be able to take out the book, because it is no longer in the catalog. When you eventually need the shelf space you will get around to tossing out the old book. That is what should happen at least.

However, as the information is still on your disk, it should come as no surprise that it can be extracted by a suitable program. This is how file recovery programs work. These programs let you retrieve accidentally deleted files from your hard drive. These bypass the master list of documents on the hard drive (they ignore the catalog for the library) and go straight to where the data is stored. By looking at the bits and bytes and the boundaries between them your documents and files can be reassembled long after they were deleted.

Now, when you discard your old or broken computer, precisely the same tools can be used to examine the data on your hard drive. If you are like most people these days, this will be a significant fraction of your entire world. Information in your email will be accessible, information in spreadsheets about your accounts and taxes, your web browsing history as stored by your web clients as you go about your day to day browsing.

Notice that I am speaking of the hard drive. It does not matter if the mother board of the computer is dead. It does not matter if your daughter poured lemonade into the DVD drive. The computer itself may be useless and may not even start. However, whatever was last written to your hard drive will be accessible to the next person who hooks up that drive to a suitable device. It is worth repeating, everything that is on your hard drive will be accessible to the next person who has physical possession of that hard drive, unless you take steps to prevent it.

Sometimes this fact can be used to extract information from the hard drives used by criminals. Hence the world of computer forensics exists. Sometimes this information is used to bail out the company that did not set up efficient backup procedures and needs to have its mission critical databases extracted from an old broken down machine.

But, most often, the storage of old data on old hard drives is a way of passing your personal information onto the next owner of your hard drive.

However, you can take steps to prevent this. Here are some of the things that you can do.

Encrypt your documents. If you use Word, Excel and so on, you can set a password on the document, so that every time that you open it you will be prompted for a password. Similarly someone who recovers this document from your hard drive in the future will be prompted for a password. This strategy has some problems, often the password encryption in general purpose applications is not very strong and can be broken by determined hackers, additionally many programs do not provide for password protection. Passwords are inconvenient in files that you open and use regularly. You are constantly supplying passwords instead of using your documents.

Use a data shredding program to delete your files. This is the best approach to maintaining the security of your data. A good program to delete individual files is called fileshredder it is free and can be obtained from www.fileshredder.org. If you use Linux there is a similar utility called 'shred'.

Use a disk clean-up program to wipe the hard drive before you part with the machine. If you want to completely clean your hard drive prior to getting rid of the machine a good program to do this is called DBAN, available from www.dban.org. DBAN requires a little more effort to use - and be careful it will completely and irrevocably wipe your hard drive. So read the instructions!

Do not recycle your hard drive with the rest of your machine. At the end of the life of your computer, take out the hard drive and have a technically savvy person make sure that it cannot be read. This sounds easy enough, but for many people tracking down a technically savvy person is a chore and finding and extracting the hard drive takes a little technical knowledge.

Use a hard drive password. If this is a laptop machine, you may be able to set a hard drive password. This will make extracting the data from the machine extremely difficult, if not impossible. It will also be quite inconvenient for you as you will be constantly supplying the password. Additionally, you will be in serious difficulty if you ever forget the password as there will be no way to reset the password.

So, hopefully you are now aware of the problems posed by data stored on hard disks and why simple file deletion is not enough to remove your information completely. If you want to be sure that information is gone, make use of fileshredder and if you want to clean up a disk completely prior to recycling or selling a machine, DBAN is the tool that you (or your IT person) will need.