It is especially important to control the disposal of information resources. Printed reports and microfilm containing sensitive information should be shredded before being thrown out. Special procedures are needed to destroy information stored on magnetic and optical media. Using built-in operating system commands to delete that information is insufficient, because many utility programs have been developed to recover deleted files. For example, the British company Pointsec Mobile Technologies purchased 100 hard drives from an online auction site and found that it could recover data from 70% of them. Proper disposal of computer media requires use of special software designed to “wipe” the media clean by repeatedly overwriting the disk with random patterns of data. Alternatively, magnetic disks and tapes can be run through devices that demagnetize them. Physical destruction of magnetic and optical disks prior to disposal may be the safest alternative for devices that have been used to store extremely sensitive data.