Created Nov 15 2005 - Updated Nov 21 2005

The Hard Disk Shred/Wipe Page


What is this page all about?
Why is it important to shred or wipe a hard disk?
I'd like to learn more about the importance of this issue?
How can I shred or wipe my disks?
How long does it take to erase a disk using DBAN?
What about a hardware solution?


What is this page all about?
A hard disk contains lots of data.
When you pass it on, you should consider shredding or wiping the hard disk to ensure the data is not easily retrievable.


Why is it important to shred or wipe a hard disk?
Shredding or wiping  is currently the only method of securely obliterating the data on your disk
Shredding/wiping overwrites the hard disk making recovering your old data very difficult if not impossible


I'd like to learn more about the importance of this issue?
An excellent News forge article is here
A great ORIELLY article is here
Security Expert Peter Gutmann has written two excellent articles:
Secure Deletion of Data from Magnetic and Solid-State Memory
Data Remanence in Semiconductor Devices


How can I shred or wipe my disks?
There are plenty of free and not free software tools for doing this
I'll concentrate on 2 free ones, Shred and DBAN

Shred
Shred is part of  the GNU Core Utilities
I run shred under Knoppix 3.9
# shred -n 2 -z -v /dev/hdxy

-n 2    Overwrite the partition 2 times with random data
-z        Finish with one pass writing of zeroes
-v        Show it's progress

Change x to reflect the IDE drive number (ie /dev/hda)
Change y if needed for a particular partition (ie /dev/hda1)
Be careful !!
# shred -n 2 -z -v /dev/hda will shred all of  the first IDE hard disk
# shred -n 2 -z -v /dev/hda1 will shred only the first primary partition of the first IDE hard disk

I also used hdparm to greatly improve the hard disk throughput
I use:    hdparm -X66 -d1 -u1 -m16 -c3 /dev/hda
YMMV

DBAN
DBAN is Darik's Boot and Nuke
DBAN is a Linux based bootable floppy/CDROM that provides an excellent shredding/wiping interface
Here's a chart outlining DBAN's erase methods, security levels, number of passes and details

Method
Security Level
Passes
Details
Quick Erase Low
1
Hard disk filled with zero's
RCMP TSSIT OPS-II Medium
8
8 drive-wiping passes with a random byte in the overwrite sequence changed each time.
DoD Short Medium 3
Makes three (1, 2 and 7) of the seven passes recommended under the DoD 5220-22.M standard
DoD 5220-22.M Medium 7
A seven-pass wipe using random characters, complements of characters, and random data streams.
Gutmann Wipe High
35 27 random-order passes using specific data combined with eight passes using random data.
Due to changes in the different data encoding schemes now used by modern hard drives, Gutmann no longer recommends 35 passes. A few random passes should suffice.
PRNG Stream Medium
High
4
8
Overwrites the drive with a stream from a Pseudo Random Number Generator (PRNG)


How long does it take to erase a disk using DBAN/Shred?
Here's my test bed
Asus A7V8X-X AMB Athlon XP 2000+ (1.6 GHz)
512 MB DDR-SDRAM PC3200
20GB Samsung SV2001H Ultra ATA/100 5400 RPM hard disk
DBAN 1.0.6


Method
Time - Hours:Minutes
DBAN Quick Erase 00:28
DBAN RCMP TSSIT OPS-II 02:19
DBAN DoD Short 01:09
DBAN DoD 5220-22.M 02:05
DBAN Gutmann Wipe 04:32
DBAN PRNG Stream 4 Passes 01:24
8 Passes 02:19
shred -n 8  -v /dev/hda
Knoppix 3.9 with hdparm -X66 -d1 -u1 -m16 -c3 /dev/hda
01:54


What about a hardware solution?

I used Goggle and found the WipeMASSter from here


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If you find an error or wish to comment please let me know