possible moisture or contamination. The fact is, during operation, the disk pack is surrounded by dirt and grease particles  that  are  circulated  through  the  air  by  the cooling fans of the disk drive; consequently, there is a definite need for a cleaning procedure, if not an actual schedule. If   your   installation   has   a   disk cleaner/certifier, learn how to use it, and you will find fewer  disk  errors  and  a  significant  decrease  in  the number  of  computer  reruns.  A  well-organized  disk management   program   will   serve   to   eliminate   head crashes  caused  by  contaminants;  decrease,  if  not eliminate, hard data checks; and decrease significantly the number of soft data checks encountered. DEGAUSSING  MAGNETIC  MEDIA Degaussing   magnetic   media—tapes,   disks,   and drums-involves  a  process  in  which  you  demagnetize the media itself. This rearranges all the 0 and 1 bits, sort of mixing them up, you might say. Normally, the only time  you  would  be  required  to  perform  such  an operation is when you must declassify (remove the data from) the media before the media can be scratched for reuse. To remove a previously recorded magnetic signal (all the 0 and 1 bits), use a concentrated magnetic field to magnetically saturate the oxide coating of the media and randomly orient all the magnetic particles. Magnetic Tape Degaussing To  degauss  a  magnetic  tape,  you  must  pass  the entire   tape   through   controlled   fields   of   alternating current to reduce the signal level of the magnetic tape’s recordings to a level which is below the capability of ADP equipment to interpret. This requires that signal level  reduction  be  performed  on  the  entire  reel  of magnetic tape, including the tape leader and tape trailer. For a tape 1 inch or less in width to be considered unclassified  by  the  National  Security  Agency  (NSA) standards,  the  signal  on  the  tape  must  be  reduced  a minimum  of  90  dB  (decibels)  below  saturation  level after  degaussing. The  manufacturer’s  recommended operating  procedures  should  be  followed  when degaussing a tape. Also, the tape degausser should be checked  at  least  quarterly  by  technical  personnel  to ensure proper operating level specifications. Before degaussing a tape, you should remove the tape   wrap-around   strap   to   prevent   the   reel   from jamming, and secure the end of the tape with a foam rubber stopper to prevent the tape from unwinding. The degaussing   operation   itself   takes   no   more   than   2 minutes per reel for a magnetic tape with a maximum one-inch  width. Magnetic Disk, Diskette, and Drum Degaussing Rigid   magnetic   media   such   as   disk   and   drum storage, as well as diskettes (also known as floppy disk), should   be   machine   cleared   (overwritten),   using   a specially  designed  computer  software  program.  Once the  media  has  been  overwritten,  it  should  be  verified (checked) to be sure the read mechanism cannot detect any  traces  of  data  information  except  the  characters used  in  the  overwrite  procedure.  Only  then  can  the media   be   considered   as   unclassified,   and   all classification   labels   and   markings   identifying   the subject matter be removed. You should also ensure the computer  operator  checks  out  the  computer  and  all related  components  that  are  to  be  used  immediately before  beginning  the  overwrite  procedure.  This  is  to  let you know that malfunctions, which could prevent the classified   information   from   being   effectively overwritten,  do  not  occur. During  the  overwriting process,  all  storage  locations  will  be  overwritten  a minimum of three times, once with the binary digit “1 ,” once with the binary digit “0,” and once with a single numeric, alphabetic, or special character (other than “0” or “1”). The current used in overwriting must be equal to that used when the data was first recorded, but not so strong that it will damage or impair the equipment. If the storage device fails in such a reamer that it cannot erase  the  data  from  the  media,  the  media  may  be declassified by exposing the recording surface(s) to a permanent  magnet  having  a  field  strength  at  the recording surface of at least 1500 oersted. Care must be taken to ensure that the entire surface is wiped at least three  times  by  a  nonuniform  motion  of  the  magnet. Care  must  also  be  taken  to  assure  that  all  tracks  are covered  by  the  center  of  the  magnet.  A  thin  sheet  of clear  plastic  (a  1-to-5-mill  sheet)  should  be  used  to prevent any damage to the recording surfaces. MAGNETIC TAPE AND DISKETTE DESTRUCTION When it comes to the destruction of magnetic tape and  diskettes,  you  will  use  the  same  techniques  as  hard copy  material.  Depending  to  the  equipment  available  to you, you will shred or burn the material, depending on the classification and the type of equipment. Because of their design, some of the shredders can not be used to shred magnetic tape or diskettes. Remember to use your local  standard  operating  procedures  (SOPs)  as  guidance 2-20