Randy could just reformat the hard drive with a single command, but (1) it would take several minutes to execute and (2) it would not thoroughly erase the incriminating bits, which could be lifted from the hard drive by a motivated technician. Because he knows which files have recorded his log-on, he executes a command that finds those files on the hard drive. Then he types another command that causes random numbers to be written over those areas of the hard drive seven times in a row.