A method of securely deleting data from a storage medium includes generating a bitmap that corresponds to unused locations on the storage medium; initiating a background process that wipes the unused locations, where the background process runs asynchronously with a user application; wiping the unused locations; and updating the bitmap to reflect that the unused locations have been wiped. The wiping replaces data at the unused locations with random sequences, with pseudo-random sequences, with data generated by a secure deletion algorithm, with application data from the user application, or with all zeros. The wiping includes repeated writing of predetermined sequences to the unused locations. The wiping replaces data at unused locations that represent portions of any of blocks, clusters and sectors, and can wipe any metadata associated with files previously stored at any of the unused locations. Upon a request for access of data from a wiped location, data that does not correspond to data originally stored at the wiped location can be returned.