wiping deleted data - BCwipe multiple passes

TigerUK · 10 May 2011 at 02:53

I'm selling a used netbook by plcing it onto an auction site, and I've always taken precautions and used BCwipe to wipe free space before selling it on.

I've noticed that bcwipe has several types of wiping with fancy government and military names, which take 10+ hours to do on a regular laptop. I was wondering what the benefit of doing 7 passes on the disc was.

I always go for 1 pass, and if that doesn't work out, just cross my fingers that nobobody malicious is going to get their paws on my data.

I'm pretty sure 1 pass is absolutely fine, but my question is why do these professional instutitions prefer to do several passes? is there an actual possibility that a wipe will fail?

edit: sorry this really belongs in the Windows software section, posted here foolishly

Brian8bit · 10 May 2011 at 03:04

I use Dban, Ccleaner and Recuva for these tasks on Windows machines. Some say that a single pass is enough. I've single passed HDDs and flash USB sticks and been able to recover data. Not all the data (I was testing for myself just how effective the programs where). But maybe files here and there where recoverable and viewable. And even after a Gutmann wipe, file names where still found by Recuva but the majority of files were corrupt and couldn't be used or viewed or executed. But their original names where there.

If I'm cleaning a drive for myself for a fresh install, I'll do a single wipe. If I'm doing a wipe with data I'm paranoid about on a disc I'm reselling, I'll do a Gutmann wipe. If there was data on the disc or stick I want absolutely no-one to have, I take it into my shed and batter the life out of it with a hammer for a couple of minutes and then take it to the recycling centre.

TigerUK · 10 May 2011 at 18:42

thanks for the info.. I didn't actually use ccleaner, I just created a new admin account, logged onto there and deleted my previous account.

The gutmann wipe will take me 10 days to complete with 35 passes, and it just feels so OTT, I've taken the middle ground and went for a 10 hour wipe.

TigerUK · 13 May 2011 at 20:32

Brian, I've installed recuva to see what data I could recover after the BC wipe run using the first option US DoD 5220.22-M(ECE) took around 15 hours to wipe each 100GB partition.

I then had a look through the drive using Recuva, and all the user data were wiped clean. I have tonnes of entries on recuva like

filename -------- path
4xx ------------ C:\?\6XX\
4XX ------------ C:\?\

I'm guessing these files are filled with random 1's and 0's too making them impossible to recover.

Maybe the problem you were having with wiping was down to using Dban? maybe BCwipe would ueild better results, because I cannot see any trace of my previously deleted data. I used the thorough scan in Recuva as well, and not just a quick scan

J.B · 13 May 2011 at 21:12

Its all about proportionate protection. For example the information on your hard drive probably has a relatively low impact, if it feel in to the wrong hands what is the worst thing that could happen? How long is that information relevant for?
When I sell a drive I normally do 1 pass on it, where I used to work we used to do a 3 pass which conformed to some standard. Either CESG or NIST or something

dynamis_dk · 14 May 2011 at 10:01

I work for IT in local authorities and our clean method used to be 7 pass's (which is 3 passes of '0', 3 passes of '1' then one last pass of random '0 or 1'

We're now required to destroy any media (hdd, flash, tape etc)... HDD's crushed so platters are bend to at least 45 degrees then melted down or shredded - all others shreaded. This is a UK Government requirement we've been asked to adhere to (afaik)