Every week, or possibly every day, there are new forums where people (with little to no experience of data recovery) discuss the merits of different methods of wiping data and destroying hard drives. One of the the frequent conclusions is that data cannot be deleted or wiped and thermatie is the only answer.
Some people will discuss, at length, the number of wipes that are required to wipe a hard drive, with answers varying from 7 to 32. Some insist that once you wipe it 32 times you then need to grind the hard drive to a find powder, and then, of course, use thermite.
These answers, as anybody who actually works in the data recovery industry will attest to are complete rubbish.
Once data has been overwritten i.e. a 0 is converted to a 1, or vice versa, then that data is gone. It cannot be recovered by software, electron microscopes, or men in dark suits. It is gone.
In addition to this, the moment that the platters of a hard drive are scratched, recovering data from them is very hard, and can be impossible. Hard drive platters are surprisingly sensitive, its just that the hard drive itself is a very good design. Anyone doubting this can perform a simple test, take an old hard drive out of your computer (one with data on, but data you don’t want), open the drive and put a long deep a scratch along the platters. Then, send the drive to a data recover company and see who can recover the data. Most data recovery companies offer a free diagnoses, i.e. you can find out for free if they can recover it.
Or, if you want to use the same service the CIA, MI5, and all the other spooks use, you can pay £100 for a diagnosis and send it to Ontrack, the worlds biggest data recovery company.
KrollOntrack recovered the data from the Shuttle, they are the company that governments use when is a major case, from the Madrid bombing to old backup tapes that contain critical data.
To wipe data do you need thermite? No. [But that would definately work!]