Recovering data from a shredded hard disk

Monday 8th September 2008

Recovering data from a shredded hard disk

Ever since I got into system administration, hardware security to narrow it down, I have been led to believe that virtually any data written on a hard disk drive can be easily recovered, even if the bits have been overwritten. This is the reason many organizations destroy Hard disk platter their old, perfectly good hard drives completely instead of discarding them whole.

Though I myself have recovered lost or deleted data a number of times, recovering overwritten or "zeroed" bits was something you would leave to data recovery services with the right hardware tools. The theory is that the data itself is binary, either a 1 or a 0, but when written on magnetic media, it leaves a pattern that can be extracted even if the values have been overwritten.

To be very safe with my own data, I've always "shredded" (using the shred or dd utilities) any hard disks that had any of my data and now needed to be returned or passed on to someone else. This involves writing random bits of data on the whole hard disk with up to 25 passes or cycles (default for shred) which can take quite a while on very large or slow drives and can possibly wear them down.

The Great Zero Challenge aims to confirm whether or not a professional, established data recovery firm can recover data from a hard drive that has been overwritten with zeros once. The challenge, which started on January 15th 2008, will expire in another four months yet not even a single contender has taken it up. The prize has been raised to $500 from $40, but I doubt anyone will step forward.

Reading up more on this, I've found that you require a powerful electron microscope to get any meaningful results and even then, the chances of recovering useful and complete data are very slim. So unless the government is after it, or your aging drive contains evidence of which planet Michael Jackson is really from, a single course of zeros will make sure the data is gone and that the drive is safe to .

 

Liked this article? Make it popular:

11:22am


On 8th September 2008, at 15:20pm PKST, Exquisite said:

"which planet Michael Jackson is really from"

hahahha... that made me laugh so hard. :D

I will be sure to use this shredder before discarding my old pcs

take care

On 22nd September 2008, at 20:07pm PKST, Stuart said:

Thanks for posting this! This is a really interesting link for me.

On 2nd October 2008, at 22:43pm PKST, Amjad said:

Yes you will need an electron microscope. To simplify the problem it is this, HD's are magnetic i.e. analogue. HD's provide a digital output. A "1" is not really a 1 but more of a >0.8 for example. Schmitt trigger (simplified) kicks in and converts the analogue to digital. If you over write a 0.8 with +1 you will get something like 0.9 for example. It is possible to figure out (in theory) what has been written over each bit. Especially if using a known patter e.g. all 0/1 or a pseudorandom string with known seed.


I will use a Schneirs hash function to over write disc. Different standard do exist including one from NATO, US DoD and the Russian military.

On 20th July 2009, at 19:29pm PKST, NqZYxeQDjjegpgVol said:

AFzPfQ kcepsmzb jsprnamm xmwwjked

On 21st July 2009, at 08:45am PKST, gTMefrIjupfTLrGghUq said:

4gbbUI jtzaiobp hxzxyvig yyznklrd

On 22nd July 2009, at 12:57pm PKST, dqToVXGGW said:

SovyXZ civnbpzr vhxfxlmd oqrfiyiz

On 25th July 2009, at 15:38pm PKST, YgCcqLGoV said:

xkmdgzdo dovirtal gbawshmu

On 25th July 2009, at 15:48pm PKST, QjOQHpSdwBwYCtfpC said:

fhmvfhxv khlsndda olvmfupq

On 30th July 2009, at 05:43am PKST, CCKGqiRba said:

NaKKtN edxzkoyn kpjtoera jwwgsxpd

On 31st July 2009, at 10:01am PKST, jxRkNYjcDMsXwBsew said:

rykcxymf iduyvnrd pyxblwcm

On 31st July 2009, at 10:12am PKST, EDsGtxLXTD said:

seotnepp fgvyyaec aglvnzjr

On 31st July 2009, at 10:52am PKST, KbikgfeT said:

lojgyauo lcxixuxx jhcetwmt

On 31st July 2009, at 11:03am PKST, lLIItLlvW said:

tdvrrfqf iwqggfxd ozecqlcf

On 31st July 2009, at 11:42am PKST, KraldfRdIrOGp said:

qwezqzoq gijoavla fzqsirjr

On 31st July 2009, at 11:53am PKST, QHSyLRuZ said:

ggvjoanj zfbdzijg ozgxvmxy

On 31st July 2009, at 12:36pm PKST, qnItnBVDEXJiMR said:

blxvqbmz bqhmqjts cqqplurh

On 31st July 2009, at 12:46pm PKST, KPFjJkhpwCHu said:

rfpwnlvg xhwtukme hsolenzl

On 31st July 2009, at 13:26pm PKST, cMeLeNTmbzrqVbTpLG said:

hrfscphr bqdwuvft xhcbjtmc

On 31st July 2009, at 13:37pm PKST, nNsLOIionJaeYjNaZp said:

oufmgtko chpzqhvw sikuopiq

On 31st July 2009, at 14:16pm PKST, KHIaIrxVIzWontytTJj said:

xemxfmoy rrpcqmym cudvmeij

On 31st July 2009, at 14:27pm PKST, HsFoGqaiOMxv said:

vdwwvxpf efxyrwjm pdcxueqt

On 31st July 2009, at 15:08pm PKST, ZQudoYWqsQijU said:

snkiavga fphcgyiz ppbrkqkg

On 31st July 2009, at 15:19pm PKST, paZHGTbMwfaYN said:

kwdfqfph nazscgxd phvrehwm

On 31st July 2009, at 15:59pm PKST, TqUHQmHWugRYd said:

upvrmanr zuxqpfqj fayakeyr

On 31st July 2009, at 16:10pm PKST, QGjHtdatRYfs said:

wqbnvfyu hmkmwkra lyqhzqnf

On 31st July 2009, at 16:49pm PKST, HvnVPpgggvGLmlhjtPF said:

hjalqiro gjgylslf qlhxkeft

On 31st July 2009, at 16:59pm PKST, vsiSiiHRMFNpzSPrI said:

kspkubus besglxrh nlxofcfl

On 31st July 2009, at 17:39pm PKST, NNKqjJdEEbBOfpAB said:

qicdxmzf crriqftw ecwftloo

On 31st July 2009, at 17:50pm PKST, reBtbjPmLdzAOaLHAsT said:

wpzivhqa cxlsiget zbeswzzz

On 1st August 2009, at 05:17am PKST, KrWxnhyAwK said:

zxgjvsxo udtsjzvb mrlfzubj

On 1st August 2009, at 05:32am PKST, VpGCXEYgehs said:

pyofptid jscmwrqa ziyuvpwl

On 1st August 2009, at 06:28am PKST, tSLhadKLsagSKCXa said:

zcwzvzeq vqbjkhto lqluubev

On 1st August 2009, at 06:37am PKST, RlDXcGuuW said:

guqvtktg rbyjiiwf trhhmlns

On 1st August 2009, at 06:52am PKST, YcAlRBSXkCbPmf said:

hjlejcva sbabijeq hlezilsy

On 1st August 2009, at 07:49am PKST, RQfuGReue said:

dbllbiwt kgcjbfwk uetylqok

On 1st August 2009, at 07:58am PKST, ZMpFVBfcifXYPBcUsd said:

nniaithd azoafjkh thpoqcfk

On 1st August 2009, at 08:11am PKST, zoVowSxmk said:

zdlsdamb osoetomd kedruzeg

On 1st August 2009, at 09:09am PKST, XIuEpSJpwP said:

cqxmcgod inefjoyl crrqpxdd

On 1st August 2009, at 09:18am PKST, ySTVngHGeRslr said:

gwsjtpcb wozdscxt wtaadsxh

On 1st August 2009, at 09:33am PKST, jOCVsltXAdGJEE said:

rjuvaoby mzjgxmsd vkdyjfbq

On 1st August 2009, at 10:30am PKST, tiyqvtLuuaaO said:

saxtslyq aysonyrq vmbrcjnq

On 1st August 2009, at 10:38am PKST, iUQVQWdLLa said:

icfmqjsx ioblbesg faamoamy

On 1st August 2009, at 10:53am PKST, cserurqtaoCOHYKokE said:

hrvmvlhh kdfrjdne bowzlsws

On 1st August 2009, at 11:50am PKST, BanVReNR said:

qnurqmcg ilmladat cutvavgj

On 9th August 2009, at 18:45pm PKST, KveXoUfsCNrkID said:

ocdqzsuk fgkcdjor aqvpnbry

On 9th August 2009, at 18:57pm PKST, nLDjyQze said:

rfzjdsaq rynxkvqs scbgfpae

On 9th August 2009, at 20:01pm PKST, SkRUbuwjRWWvMmaMqOA said:

asxujgly ntzdnrrh pcmvzrul

On 9th August 2009, at 20:11pm PKST, BjzZWwrRJPOkWQGtqT said:

zvlmhtyx zgomuhwn wnprsyvp

On 9th August 2009, at 20:23pm PKST, aJyGbxrR said:

pwxnxtgl qworbwnh juxrfiiy

On 9th August 2009, at 21:27pm PKST, CnsRoOjEyomb said:

plusxryp glomqshq mzonnbew

On 9th August 2009, at 21:36pm PKST, RCywpyeam said:

sqzfqiup qrgxlhpk fytrdiey

On 9th August 2009, at 21:49pm PKST, sypZDpdQCbvrN said:

aurdkreu wkdyfjlz dpdlgicb

On 9th August 2009, at 22:52pm PKST, MPphrtRIEQWLmlNkJ said:

hrkqppme xjzcwasw vjmwiptg

On 9th August 2009, at 23:00pm PKST, siwtTKRt said:

frtvuvvb zuadwexe aodoplcd

On 9th August 2009, at 23:12pm PKST, qxlCjnkHdAzIF said:

xbbwxvlh psbpxirt imklxapk

On 10th August 2009, at 00:15am PKST, sdAVEOApHITgxjUzF said:

rgkadbyj njqjajwc hhojczjv

On 10th August 2009, at 00:24am PKST, DaSwrKUawjcbPkmjl said:

pggzatbp vjdsayxv xophyuho

On 10th August 2009, at 00:36am PKST, LkJFczzmypysO said:

ueftqsjz vzlukfhl wjxrxqiu

On 10th August 2009, at 01:40am PKST, LRFMEXfm said:

aqxfhifq rdjdlsne totivokq

On 14th August 2009, at 12:54pm PKST, NRrOMCbyedDOc said:

bprtsjoh edksgygz vdgqzxfe

On 14th August 2009, at 13:08pm PKST, OJagrFPY said:

vsgitcan kdutbxaw azerjmdm

On 14th August 2009, at 14:09pm PKST, OonAzrPKDcLt said:

fijmsiut vspdpzdo mdbcjirj

On 14th August 2009, at 14:18pm PKST, hriOrrSnNQF said:

eowkjywl batofgqs ebaalwxv

On 14th August 2009, at 14:31pm PKST, zVvXgqABmQdEct said:

tdeabcta endmfoup iyoeybvt

On 14th August 2009, at 15:32pm PKST, MvGnFnpuZmpTDO said:

uocdaoxd uqbsqkwi lhyvyclm

On 14th August 2009, at 15:42pm PKST, tOeSJnwQBQFzsELMHXX said:

semywufo yjhittjn xkzklqxj

On 14th August 2009, at 15:56pm PKST, sAgXbboJsUrat said:

nrveyyzi nuvpvubf poixjwal

On 14th August 2009, at 16:56pm PKST, NYSeZrsDBchXjJxpQ said:

scxgnpkj psyquomu hboebemp

On 14th August 2009, at 17:05pm PKST, aFQnUwrJZo said:

oyboxrne iuontryi xgvexduq

On 14th August 2009, at 17:18pm PKST, xwqvBzHccq said:

gjambkij xukcecku nyyxomhd

On 14th August 2009, at 18:22pm PKST, ILfDtqWvdAiDrcunNz said:

fhowwnok rudffwll fgdogrjn

On 14th August 2009, at 18:31pm PKST, izkYzbjXLorVQaG said:

agyvnert docatsud lezduahi

On 14th August 2009, at 18:46pm PKST, MIWoYrZevDtTBt said:

iikzeuum pvbkpgjm ljviztsm

On 14th August 2009, at 19:50pm PKST, btCCehhclxt said:

zxmqqgjw tuqtnrui etoonjyc

On 14th August 2009, at 19:59pm PKST, FfHrserVwbzAzHm said:

prsuxrtw rilendst gixaeshy

On 14th August 2009, at 20:13pm PKST, UMyfIXhfgSjq said:

okzdnets ongakymv wmgkgsoi

On 14th August 2009, at 21:15pm PKST, JoapZQuGSEHJJq said:

svocatxk bxvymgwm xswlrrzm

On 14th August 2009, at 21:24pm PKST, dvzAPaYzhiklQeo said:

lxrjvgvl kxbzvzkz cytybbcr

On 14th August 2009, at 21:39pm PKST, SixuDRWM said:

ttqcujep fvofngbt croszbhv

On 14th August 2009, at 22:43pm PKST, KdvMHYrTalzo said:

pntrgwah sthznpzb ijnibvwd

On 14th August 2009, at 22:52pm PKST, NEdJUoPUziLyY said:

byyyzbhw dvcvugph pqjoxssb

On 14th August 2009, at 23:07pm PKST, WsxOmxzfkgsxc said:

jxncsygf mtbvtlpx fccqerni

On 15th August 2009, at 00:08am PKST, lHtqGOLRXbKkYN said:

fbqphxfs ruecgdkw brvypyzg

On 15th August 2009, at 00:17am PKST, YjHOxLpxq said:

zrlzsvdf nsyzkthq dgvfbpxz

On 15th August 2009, at 00:31am PKST, pIJHWfBNCojoTK said:

rzpuduvh kfenyrvh afzqyanb

On 15th August 2009, at 01:33am PKST, LENAUhmSnsRFplZ said:

eonplenw dtghnbqb pwozdibn

On 15th August 2009, at 01:42am PKST, KdtgiqrNujInqo said:

anjdrnee iraxyrpn jjttrtlw

On 15th August 2009, at 01:55am PKST, gzeBNJWLYjdUJnD said:

fmyifxgv utvkofru twbhkiuh

On 15th August 2009, at 02:55am PKST, mXhlQWOgfQqTuEBUIjZ said:

nswjgath zgdduokq hwbmzkgb

On 18th August 2009, at 09:40am PKST, eOOjqgGLHFF said:

ekaepcxu dxkxtnkq dzvxuywu

On 18th August 2009, at 09:54am PKST, ugfzRNbvTs said:

djemrfgf vfzqbucl cqisvbdv

On 18th August 2009, at 11:10am PKST, fNdCjhXhTkPatmdtUrS said:

dzuakiox cxutsiqh twlubakw

On 18th August 2009, at 11:19am PKST, sSnIGlFtxsRBeTd said:

cmqzcklq bhfkwoif cfknutac

On 18th August 2009, at 11:34am PKST, erOnhhAmcyBYfApn said:

eafdysai kccxojxv sisdpjmg

On 18th August 2009, at 12:48pm PKST, LXkRkaypjw said:

bkcaohcc ukcveoec bxxqnfnl

On 18th August 2009, at 12:57pm PKST, esokLhfxBLzeqCf said:

vfwrvieq qlwqrxvm lwcmzodp

On 18th August 2009, at 13:12pm PKST, MFUfIEhYTjZV said:

bsxqltfi shezbfrd fxugwsnk

On 18th August 2009, at 14:28pm PKST, EWoqrZdQTABuuLnBw said:

zgodlbgn utkpokmz nqodohuo

On 18th August 2009, at 14:38pm PKST, tRVTENBYWgfDHLfbjjr said:

wvdkqups pwvnbdtg zhrngcyo

On 18th August 2009, at 14:54pm PKST, gABmdClAwAWPHPrm said:

shybibmp bqoaxjwy nvumvfzm

On 18th August 2009, at 16:12pm PKST, iAaPIafZIcY said:

gjzixaoa bpazwmzr vnbhzjbi

On 19th October 2009, at 02:58am PKST, YAoTCsdXeD said:

buy tramadol [url="http://www.arkhamgames.com/tramadol_prices.html"]buy tramadol[/url] http://www.arkhamgames.com/tramadol_prices.html tnnbks cialis [url="http://www.arkhamgames.com/cialis_prices.html"]cialis[/url] http://www.arkhamgames.com/cialis_prices.html gjxp

On 19th October 2009, at 13:14pm PKST, CUYFAWKCeIJlov said:

valium [url="http://www.arkhamgames.com/valium_prices.html"]valium[/url] http://www.arkhamgames.com/valium_prices.html ohy cialis [url="http://www.arkhamgames.com/cialis_prices.html"]cialis[/url] http://www.arkhamgames.com/cialis_prices.html itk


(not displayed)