A “normal” data erasure does not provide sufficient protection against unauthorized access to the supposedly erased data. In such an operation, only the allocation reference is removed from the table of contents of a data carrier, and an attribute is set to the data which is no longer required, which allows the data to be overwritten in the future. However, all erased data still exist. It is therefore possible to read and restore deleted data with simple methods.
Even after a hard disk has been formatted, it is possible to restore the data previously stored on it at any time. Even performing low-level formatting does not guarantee secure data erasure or destruction.
Secure Data Erasure
A complete, secure data erasure – which does not allow restoration – is only guaranteed, if a data carrier has been overwritten several times. As a rule, the overwriting is carried out using different bit patterns. At present, various methods of data erasure are considered secure.Data erasure standards