Nuke that old hard drive!Nuke that old hard drive!

Alan GermanOttawa PC Users’ Group

Hard Disk Storage

Bits, bytes, blocks, clusters,sectors, tracks, and platters

Disk Files

Files may be stored in multiple blocks.

Files may be contiguous (Red),

or fragmented (Yellow and Blue)

File Pointers

The operating system keeps track of the name and location(s) of each file

FAT uses a File Allocation Table

NTFS (New Technology File System) uses a Master File Table

Delete a File

Windows resets the file pointers to locate a deleted file in the Recycle Bin (a special folder)

“Deleted” files can easily be restored to their original location (folder)

Empty the Recycle Bin

Windows resets the file pointers tomark that the file has been deleted (removed from the Recycle Bin).

The actual data contained in the fileis still stored on the disk platter.

The data can be recovered using specialized software.

Secure Erase

Overwrite the blocks containing data from a deleted file with zeros (zero-fill)

Need to overwrite every block of data in the file – rather than just the file pointers.

The process is automatic – but, it takes time!

Not-so-secure Erase?

Sophisticated file recovery systems may be able to see “patterns” in the magnetic media even for zero-filled blocks of data.

Need a scanning electron microscope?

Use multiple overwrites (passes) – takes much more time!

File/Disk Shredding

Two considerations:

(1) Shred deleted files (free space)

(2) Erase entire disk (containing a “running” version of Windows)

File/Disk Shredding

(1) Select files/disk to be shredded.

(2) Take extreme care with the selection – there’s no going back!

(3) Choose an algorithm/number of passes

(4) Start the shredding process

(5) Pour a beer – or two!

File Shredder

Add files/foldersfor shredding

…or, shred all free space

Shred !

HDShredder

DBAN – Darik’s Boot and Nuke

Solid State Drives

There are two ways to safely dispose of unwanted SSD’s:

(1) Use the drive manufacturer’s SSD utility (e.g. Samsung Magician)

Solid State Drives

There are two ways to safely dispose of unwanted SSD’s:

(1) Use the drive manufacturer’s SSD utility (e.g. Samsung Magician)

(2) Give you old SSD to Alan who will erase it for you and install it in the super-fast RAID that he wants to build!

Secure Erase

Finally, if all else fails…