Search on the internet and you will find a plethora of theories which suggest that data can never really be erased. One of the most common is Peter Gutmann’s theory that data can only be erased after thirty five passes. However this is just a theory and never been proven. So can overwritten data really be recovered? Here at Data Recovery Specialists, we have been trying to recover overwritten data for decades and never succeeded. This is because overwritten data simply cannot be recovered. A computer scientist named Peter Gutmann caused lots of controversy when he published his white paper claiming that overwritten data could be recovered. The basis of his theory was that using magnetic force microscopy a sensitive enough instrument would be able to interrogate subtle changes in magnetic variations – even where the polarity of binary magnetic returns have been altered. He claimed that to completely eliminate thes evariations, a total of thirty five passes or overwrites would be required. Some credit should be attributed to Peter Gutmann, because in theory this could be possible. However, no instrument has ever been manufactured and the theory has never been proven. So is this the stuff of science fiction? Yes and no! In the future an instrument might be developed to read these subtle variances, but this would be a long way off. By the time any instrument had been developed, magnetic recording would probably be defunct anyway! Has NASA or some other agency developed an instrument to read overwritten data? This seems pretty far fetched. Firstly what economical value would this hold and secondly, even if they had – the cost would be prohibitive for general users. Nevertheless, we see Peter Gutmann’s theories raised in many computer forensic reports. Data Recovery Specialists are often engaged to provide a second opinion on electronic evidence and you would be surprised how many ‘experts’ actually rely on these theories as evidence. So how can I make sure my data is never recovered? I would suggest two methods. Firstly a low level format or secure erasure program will overwrite all the data. After this, physically destroy the hard disk drive. Simply hammer a screwdriver through the chassis and make sure there is an entry and exit hole. By shattering the plattere, there is no data recovery company in the World who will be able to recover the data!