Over the last two weeks I have spoken about data and how the size of data is defined. One issue that is always an issue when it comes to data on your computer is when it comes time to update or dispose of a PC. The data that is on a local hard drive can be confidential or private or downright embarrassing! Making sure that other people don’t have access to that data is of varying importance to people – but most would agree that they would prefer other people not to see that data.
It sounds simple – just run the format command on the hard drive and then sell or dispose of your old computer. Wrong! Format is a very simple command that doesn’t actually remove any of your data – it just removes the addressing for your data. Confused? Think of it this way.
Imagine you run the local Post Office. There are houses throughout the city and the post office knows where to find those houses. If the post office suddenly lost the locations of all the houses in a city, it would not mean that those houses cease to exist. The way data is retrieved from a hard drive is similar. The data is spread out across the hard drive and the File Allocation Table (FAT) knows where to find that data. When you format your hard drive, it simply removes the information from the FAT but leaves the data on the hard drive. It is a relatively simple process for a sophisticated data retrieval program to piece together the data on a hard drive and rebuild a FAT with most data able to be retrieved.
So formatting a hard drive is not a great option when it comes to disposing of your hard drive.
Some people like a more physical approach. Take a hammer or drill to a hard drive and physically destroy it. While this sounds good in theory, unless you destroy every single piece of a hard drive platter, some data would still remain. Admittedly, it is quite difficult to retrieve data from a half-destroyed platter, but the data remains. Some people have used a large electromagnet to destroy data on a drive with limited success. With Solid State Drives (SSD) becoming more common, a physical approach is much more difficult. To fully destroy the data on a SSD, it would require every single piece of memory to be destroyed. Unless you want to run your SSD through an industrial shredding device, this isn’t that practical.
Luckily there are software solutions. The BIOS of some computers will allow you to securely wipe a hard drive – but these can be a little clumsy to access. There are also a variety of applications available that will securely wipe your data. The one that I have typically used (and recommended) is called sdelete (standing for Secure Delete). You will remember from last week data is made up of a series of bits that are either a one or a zero or yes and no or, technically in the case of a hard drive, a series of magnetized or demagnetised areas. A secure deletion program will write over the entire hard drive space with a ‘one’ and then follow that with an entire series of a ‘zero’ and then repeat the process. After the drive has had this treatment a number of times, it is very difficult to recover any data from the drive. More importantly, rather than completely destroying a drive, the drive could be used by someone else and leave you with the confidence that all of your data is now safely untouchable. Of course make sure you have copied or backed up the hard drive first!
So the next time you want to remove all of that information, maybe leave the hammer and magnet behind and use some clever software.