Single Drive Wipe Protects Data 625
ALF-nl writes "A forensics expert claims that wiping your hard drives with just one pass already makes it next to impossible to recover the data with an electron microscope." But that's not accounting for the super secret machines that the government has, man.
One wipe is not enough. (Score:5, Funny)
One wipe is never enough.
Didn't your mommy teach you anything?
Especially true after Taco Bell.
Re: (Score:3, Funny)
Re:One wipe is not enough. (Score:5, Informative)
Evidence of what?
You know it is often important to hide data that isn't involved with anything illegal. For example: Credit Card numbers, social security numbers and other personal information, trade secrets, personal journals and diaries that you don't want other people reading. There are many MANY reasons to want to wipe data that doesn't implicate you in a crime.
Re:One wipe is not enough. (Score:5, Interesting)
There are many MANY reasons to want to wipe data that doesn't implicate you in a crime.
Hiding your data is important to prove your innocense (or support, at least). Imagine they "find" some data in your "possession" (officer swears the DVD of images was on your desk). Or your soon-to-be-ex left it to settle a bitter custody dispute. Now imagine every bit of your data is encrypted beyond their comprehension. Will a jury believe that you have everything - including your inane personal diary - encased beyond their reach but left super-incriminating evidence out in the open? Unless they can tie that DVD to you via a purchase, I think you have a good case. Imagine any other instance where someone wants to manipulate your data to their advantage. Like it or not, encryption/wiping/security is to prevent implications in crimes. This is true whether or not you have committed any.
Learned it on "Red Dwarf" (Score:5, Funny)
"One up, one down, one to polish."
Dave Lister
Re:One wipe is not enough. (Score:4, Insightful)
Like the Lemur King Julian said in the movie Madagascar:
"Who wipes?"
Seriously though, anyone sufficiently interested in protecting data can do it in numerous ways.
I used a script to sanitize drives used in forensic collection. First pass writes from /dev/urandom, second pass writes from /dev/zero.
When drives died or became unuseable they would meet a sledgehammer moving at high velocity.
Re:One wipe is not enough. (Score:4, Funny)
I use a script that writes random files from a 6TB collection of porn. That way, when somebody does find the drive it will be impossible for them to argue that I overwrote it with porn.
Why is this drive filled with 2TB of porn? Answer: Why NOT?
Why do you have to 10 drives filled with the same porn? Answer: My backup policies force me to protect data relative to it's importance. Next.
Did these drives always have porn on them? Answer: Absolutely.
Most juries would buy those answers in a second.
Re:One wipe is not enough. (Score:4, Funny)
and both female slashdotters should remember to always wipe front to back
My wipe is better :-) (Score:5, Interesting)
Disclaimer:
The NSA has no jurisdiction here in Australia, (yet) and...
They would probably be bored by the contents of my drives anyway, and...
Yes, I am aware that that temperature will demagnetise the platters, but...
It's good fun to do anyway: shiny hot things and lots of noise.
Re:My wipe is better :-) (Score:5, Funny)
Re:My wipe is better :-) (Score:5, Funny)
Re:My wipe is better :-) (Score:5, Funny)
At which point the NSA turns it over to the CIA who have devised a powerful tool for data extraction, waterboarding. Fortunately for you the technique will be outlawed tomorrow.
Re:My wipe is better :-) (Score:5, Interesting)
I was the sole IT guy at my last place, a financial institution that went through a large amount of defective and obsolete hard drives. Not wanting to spend the time erasing the drives, I would just take them out back and hit it with a sledge a couple times until the platters exploded.
As a financial institution, we were subject to frequent audits, one of which dealt with our data destruction methods. I described our "process" to an auditor once, he laughed and asked what our real process was. Still not believing me, he brought up the same question to one of our VPs. Her straight-faced answer: "Ive seen him out in the parking lot with a sledgehammer a few time, I always wondered what he was using it on."
The next year, they sent a different auditor.
DoD Science (Score:5, Insightful)
That's why the DoD has lowered their standards to a single fixed wipe and to prove it is going to send all of their super secret hard drives to china to be proven that the data is unreadable.
Because the DoD makes ALL its decisions based on sound science. That's why the Air Force took over the CIA's sponsorship of remote viewing in 70s, why the Navy funded research into cold fusion and anti-grav, and why we're buying hand-held polygraphs for troops in Afghanistan.
I mean, I had the same knee jerk suspicion, but I'm not going to hold up the DoD's standards as proof of anything but potentially reasonable paranoia. The Pentagon has a long-demonstrated sweet tooth for junk science.
Why are we still discussing this?! (Score:5, Insightful)
Just use encryption (of your whole drive or partition) and forget about wiping it.
It's not that hard. For example, several modern Linux distros support encrypting your entire installation out of the box.
Re:Why are we still discussing this?! (Score:5, Funny)
Sadly, it's best just to physically destroy the drive after use. I suggest a two-year old child just after its nap ought to do the trick.
Re:Why are we still discussing this?! (Score:5, Funny)
I dismantle mine and make those cool clocks out of them for xmas gifts. A couple have it where the platters are mounted on a spindle also over a mirror, and move counter-clockwise. So far, only two epileptics have succumbed to the effects.
Re:Why are we still discussing this?! (Score:5, Funny)
You sure dismantling two-year olds is entierly legal? Not to mention making clocks out of the remains.
Re: (Score:3, Informative)
Re:Why are we still discussing this?! (Score:5, Funny)
I suppose an attacker *might* not be able to recover the data if you skipped the last step, but why take chances?
Re:Why are we still discussing this?! (Score:4, Funny)
Incomplete procedure! ....the nearest start that is about to go supernova next to a supermassive black hole that wormholes to an antimatter universe.
Get it right, damn it!
Re:Why are we still discussing this?! (Score:5, Funny)
I used to do that, but it's a weak procedure. People can infer what you've been up to by the lengths to which you will go to wipe your drive. Once you push the planet into a star, there are only a few possibilities for what was on your drive. (Shame on you.)
Re:Why are we still discussing this?! (Score:4, Insightful)
Re: (Score:3, Funny)
Whatever.
There's nothing on my hard drive important enough to steal (I keep all my records in a safe). Unless somebody has a strong desire for 50 gigs of women riding sybians or playing with vibrators?!? I'm not sure why you'd want to steal that which you can get for free via bittorent.
Re:Why are we still discussing this?! (Score:4, Interesting)
Re:Why are we still discussing this?! (Score:5, Funny)
Re:Why are we still discussing this?! (Score:5, Funny)
Child kills drive, drive kills child... (Score:3, Funny)
The problem there is occasionally the drive wins or claims a draw by destroying the child as well.
Part of most if not all HDDs fall well under the "choking hazard" category.
Problem? I really don't see a down-side here...
Re: (Score:3, Funny)
That's all right, you may not have to worry if it's a 1TB Seagate drive. They self-brick.
Re:Why are we still discussing this?! (Score:5, Insightful)
Encrypting it is definitely a good idea, but not as a replacement for wiping it.
Re: (Score:3, Interesting)
while it would theoretically take thousands of years to brute force it, random chance has them guess the right sequence on the first try (it could happen). You wipe the data though, and there is no chance for anyone to get it.
If we are to totally forget the order of magnitude needed for random chance to guess the key at first try then we can say that by chance "they" could actually guess your data at first try! Even if you wipe the data! Even if you vaporize your hdd!
Re:Why are we still discussing this?! (Score:5, Informative)
So the GP is right: use disk encryption instead of relying on time-wasting/manual/unreliable data wiping !
Re:Why are we still discussing this?! (Score:4, Funny)
Yep. They'll never get my data. It's all encrypted with the superior ROT13 encryption method. Twice just to be sure.
Re: (Score:3, Informative)
According to Bruce Schneier [schneier.com]:
We've never factored a 1024-bit number -- at least, not outside any secret government agency -- and it's likely to require a lot more than 15 million computer years of work.
So even if the usable computational speed of processors doubles in the next few years, it would still take at least 7.5 million computer years of work. You might have that much time (or maybe you have 7 million computers) but I don't.
No, increased computational speeds won't make factoring extremely large numbers feasible (at least, not anytime soon). The only thing that will do that would be finding some algorithm to do it - and if you figure that out, you'll deserve every awar
Re:Why are we still discussing this?! (Score:5, Informative)
Add a wipe to the encryption and you may be safe.
The old problem with multiple wipes depended on the fact that there were rather large tolerances, but modern drives are very close to limits caused by physics, which means that it's a lot harder to extract wiped data.
If the data also was encrypted it will probably be impossible to re-create since there always is a level of loss even at recovery. For unencrypted data this may not be a big problem and it can be rectified by hand, but for encrypted data it will upset the whole packet that was encrypted.
But in a majority of cases a single wipe will be sufficient when the hardware is sold as surplus, since it's not easy to track and find out if a certain drive contains anything of interest.
Re: (Score:3, Interesting)
Just to point out that we have to be abrest of the limitations of our chosen encryption scheme. Several of the IT Foresincs have started to exploit some the weaknesses that, while they may not be able to de-code infromation, might be able to identify that encrypted information is there and even what type of infromation might be encrypted.
Legally, in some places, like the UK, you do not have the legal option to not disclose your encryption keys. Your only hope of keeping the government out of your pants is
Re: (Score:3)
I use LUKS, which uses anti-forensic techniques for storing a copy of the key (encrypted with the user's password) in a header. The header is about 1 kb (see payload offset in cryptsetup luksDump). Finish with a drive, write random data over the first kilobyte of it, and if you trust 256 bit AES, your data is gone.
If it 'snot good enough for the feds... (Score:5, Insightful)
1) next to impossible != impossible
2) if the feds require multi-pass wipes for non-classified data and media destruction for classified data, why should I settle for anything less?
OK, maybe this guy is right and maybe the feds are behind the times, but I'd like to see multiple independent studies come out and say this before I'm getting rid of my drive sanitizers. I mean, we all know what happens to societies when they get rid of their equipment sanitizers [tlb.org], don't we?
Re:If it 'snot good enough for the feds... (Score:5, Insightful)
Unless you work for the government or military, no one would be interested enough in the data on your drives to go through the effort and cost of doing the forensic investigation to find out what was on your hard drive before the wipe.
For those of you in Rio Linda, nobody cares about you, or your data, unless you work for the government or military.
Re: (Score:3, Insightful)
Yes, because we are all so fully aware that the US government only ever worries about REAL security, and not security theatre.
Re:If it 'snot good enough for the feds... (Score:4, Insightful)
Re:If it 'snot good enough for the feds... (Score:4, Informative)
Well, the feds only specify that unclassified drives be wiped. Classified drives (that is, hard drives with classified material on them) must be destroyed.
Incidentally, a lot of data on hard drives is user-inaccessible due to the hard drive remapping bad sectors. Only a low-level format will touch that data--not application-level wiping tools.
Re: (Score:3, Insightful)
.....why should I settle for anything less......
because as a /. member it is highly unlikely that your deep dark secret data is worth the effort it takes to recover it after a single pass wipe. Anyone who posts on /. has, by definition, no data the NSA, KGB, Gestapo or any other such entity could possibly be interested in.
Re:If it 'snot good enough for the feds... (Score:5, Funny)
> Anyone who posts on /. has, by definition, no data the NSA, KGB, Gestapo or any other such entity could possibly be interested in.
I am Osama Bin Laden, you insensitive clCARRIER LOST
Re:If it 'snot good enough for the feds... (Score:5, Insightful)
Because the government is rife with paranoid, bureaucratic nitwits with more motivation to be "safe" than is scientifically prudent, and far more motivation to further their own careers?
And I add bureaucratic for very pointed reasons. In the beginning, suppose they had a competent CS guy deciding the policies for HD erasure, he probably figures a single zeroing is sufficient. And at the time (perhaps now too) he's correct. Then his successor wants to make in impression and put some bullet points on his resume, so he makes a big stink about "increasing security through a continuing commitment to data erasure" or some buzzword nonsense. Let's say this guy was a friend or relative of the previous guy - and not necessarily as competent. Now this did fuck all for actually making the data any harder to get at, but it furthered his career just a tiny bit. Now add 3-4 repetitions of this to the mix and you can see how the policies got to be so ridiculous. Now I am making all this up, but to me, this seems far more plausible than recovering overwritten data on a hard drive. How many times have you had trouble with your drive accidentally reading previous data from it? You know, with a drive head that was designed, redesigned, and improved over 50 years to read data from that disk.
I don't get why people often think that the US government has super awesome technology that borders on magic in the field of computer science. In my experience they were 30+ years behind the times in some areas. Some better, some worse.
The government is just made up of people. Like everyone else, so there's lots of human error. And since they get paid through taxes and don't have to worry about profits, they have little to no motivation to do a good job if their superior doesn't make them. It's why the government is into contracting these days, they get the job done quicker and better for less money because (in most cases) they have competition.
Re:If it 'snot good enough for the feds... (Score:5, Informative)
There is *no* way to recover the data on a modern drive after a single wipe. It is actually impossible. It cannot be done.
The reason is simple - although you may be able to detect a tiny tiny bit of data from the previous recording, you've no idea how strongly overwritten it is. Now, with old drives which used simple on/off pulses to write data to the disk, it would be possible to see if the bit you're looking at is a little higher or lower than it should be, and infer the previous value from that. Modern drives use a system similar to QAM - quadrature amplitude modulation - to pack more bits of data into each transition on the disk. Since the signal is essentially analogue, you'd need to know how badly degraded the print-through was. You can't do this, so you can't recover data after it's been overwritten even once.
Re: (Score:3, Insightful)
Re:If it 'snot good enough for the feds... (Score:4, Interesting)
You are overstating the case. In many instances one can make good guesses at how strongly overwritten it was. This works particularly well if the data being recovered is in some well understood format where one can look for markers. Say is there a sequence of 000s which act as a header? do we expect to see the sequence CR LF every so often?
http://www.heise-online.co.uk/security/Secure-deletion-a-single-overwrite-will-do-it--/news/112432 [heise-online.co.uk]
They concluded that, after a single overwrite of the data on a drive, whether it be an old 1-gigabyte disk or a current model (at the time of the study), the likelihood of still being able to reconstruct anything is practically zero. Well, OK, not quite: a single bit whose precise location is known can in fact be correctly reconstructed with 56 per cent probability (in one of the quoted examples). To recover a byte, however, correct head positioning would have to be precisely repeated eight times, and the probability of that is only 0.97 per cent. Recovering anything beyond a single byte is even less likely."
Multiple reasons (Score:3, Informative)
One reason they require it is simple paranoia. The lengths you go to protect something depends on the value of the thing you are protecting and thus the lengths someone might go to get it. Same reason they use lots of armed, highly trained agents to protect the president. The president is extremely important to the nation and people will go to great lengths to harm him. When you are talking about classified data, you go to the paranoid extreme.
Another reason is inertia. These rules were written back when dr
Data destruction advice of the week (Score:5, Funny)
I thought a few weeks ago we were supposed to drill holes in the drive platters and fill the case with thermite, then drop the whole computer into the fires of mount doom.
This week, a one pass wipe is enough.
Re:Data destruction advice of the week (Score:4, Funny)
Next week they'll discover a new alien technology and the security experts will be advising us to nuke the drive from orbit. It's the only way to be sure...
Re:Data destruction advice of the week (Score:5, Insightful)
It's the difference between what slashdotters enjoy doing to old hard drives and what's actually required to securely destroy the data on them.
Re: (Score:2)
Setting a drive up on its side and whacking it is usually enough to bust it and get the platters out. 8-9 years ago, the platters melted easily enough under flame of a plumber's propane torch, it was some type of pot/white metal I suppose. Last time, they didn't melt so I put them on against a sand belt grinder.
A little paranoid I suppose.
Re: (Score:2)
The pace of technology is astounding. I wonder what next week will bring.
Re:Data destruction advice of the week (Score:5, Funny)
Having fun with thermite and a hard drive (Score:2, Informative)
Hard drive meets Mr. Thermite.> [youtube.com]
Not surprising (Score:3)
it is not like you can have 2 values for a single bit at the same time.. and density is so high these days that it makes sense to have a single write wipe the previous data forever.
Conflict of interests in article (Score:5, Insightful)
The guy's a forensics expert. Of course he's going to tell you one wipe is enough. If you do more than that, he might be out of a job.
I'm surprised he didn't say "It's cool man, just write 'DELETED' in sharpie on the case and your drive will never function again. *snicker*"
Sure... (Score:5, Interesting)
That's what they WANT you to think.
In all seriousness. If the government wants to get information, they are not going to the trouble of an electron microscope to look at your hard drive. I'm sure they have other methods of extracting the information they want. While this information (about how many wipes you need) is interesting from a theoretical point of view, it is useless from a practical one.
some subject (Score:5, Interesting)
I thought this would be fairly obvious from the fact there doesn't exist any recovery services that will recover zerod out data for you, at most they can usually try to recover data that has been deleted(forgotten) by the operating system.
Re: (Score:3, Interesting)
It relies on the fact that the delete portion of the trash doesn't actually touch the disk so much as it tells the computer those areas of disk are free to be used. I heard that Windows tends not to touch those regions for a while while Linux usually makes use of those first. But I don't remember if the issue was FAT/NTFS vs ext2/3 specific.
Re: (Score:3, Insightful)
DD is probably the best bet for discarded/ebay'ed drives. I can't think of anyone who has the time or resources to dig up my data. If you're a fortune 500 company, or an international drug/arms/people/whatever smuggler, then you probably want to just go ahead and shred the drive [flixxy.com]. That way you don't have to worry about Joe skipping out early on Friday and forgetting to wipe the out-going CEO's drive.
For the rest of us, just think about the economics of it; what criminal organization has access to a lab fu
We need mythbusters! (Score:5, Funny)
Re:We need mythbusters! (Score:5, Funny)
"Well there's your problem!"
Also (Score:3, Funny)
Lies (Score:5, Funny)
Last month my grandma asked for a new laptop and prior to putting her old HP on ebay I wiped it via Gutmann 35-Pass method, way above DoD and NATO standards, so her ultra-secret vanilla cake recipe could remain a household secret.
Re:Lies (Score:5, Funny)
Using a Gutmann 35-pass wipe is like cleaning your sink with bleach, shampoo, baby wipes, ammonia, laundry detergent, insecticide, paint remover, furniture polish, glass cleaner, body wash, whiteboard cleaner, and gasoline.
Using full Gutmann suite is a waste of time. You only ever need the 1 or 2 runs that were designed for your drive.
Essentially, you did the computing equivalent of trying to clean a barbecue grill with saline solution.
Re:Lies (Score:5, Funny)
Using a Gutmann 35-pass wipe is like cleaning your sink with bleach, shampoo, baby wipes, ammonia, laundry detergent, insecticide, paint remover, furniture polish, glass cleaner, body wash, whiteboard cleaner, and gasoline.
Oh, so you've seen my sink?
Re:Lies (Score:4, Informative)
Pre-scrambling drive (Score:4, Interesting)
It says data written to a pristine drive is much easier to access.
If drive-manufacturers wrote random data to their drives 2 or 3 times before shipping, I wonder if this would help?
Combine this with OS-level "overwrite with random after delete" or, to allow for "oopsies," delayed-overwrite after delete but before next use, the problem of "ghost data" in unallocated drive space could mostly disappear.
Of course, there are other issues, like data internal to a file that is no longer current, data in paged-memory files, and data on backup media, but that's outside the scope of the "I deleted the file, it should be gone but it's not" problem.
One Wipe...pppphfhtpt! (Score:5, Insightful)
[pulls tinfoil hat tighter over head]
Sure, that's just what they want you to think.
If you are able to do it (Score:5, Interesting)
which is surely worth the time and effort involved in something like this.
Re:If you are able to do it (Score:4, Informative)
Wow, they put the prize money up! Last time we discussed that here [slashdot.org], the prize was a whopping $40.
Re: (Score:3, Insightful)
> which is surely worth the time and effort involved in something like this.
Hardly. I think that you'll find that the machines required rent for more than $500/hour.
Define next to impossible (Score:3, Insightful)
Re:Define next to impossible (Score:5, Insightful)
Define next to impossible
The researcher did. From TFA:
Recovering a single byte of data, for example, on a used drive is successful less than one percent of the time, he found. Accurately recovering four bytes, or 32 bits, of data only works nine times out of each million tries.
So, 1 specific byte of data could be recovered 1% of the time, 4 bytes -> .0009%.
Extrapolating to 10Mb is about 1/10^(10^6 / 8)=0% according to my calculator which keeps goes to 10^-324. So, I think 'next to impossible' is a pretty accurate term.
Methology, do you know it? (Score:3, Interesting)
His chance of retrieval was trivially above the random 50%.
You just could guess _any_ content with the same probability.
Simpler approach (Score:4, Funny)
Depends on your crime (Score:4, Insightful)
It seriously depends on your crime as to how far police will go to obtain data from a hard disk.
If, for instance, to kill no more than three people in cold blood. They won't even look.
If, you have a few ounces of pot, the DEA will use the FBI forensics labs.
If you have a history of violence and have beaten countless women, they won't even look.
If you've given more than a few hundred bucks to an Islamic charity, the NSA will step in.
If you bilk hundreds or thousands of people out of millions of dollars, they won't even look.
if you are accused of fighting on the train in San Fransisco, they'll just hold you down and shoot you in the back. Fuck the computer.
Re:Depends on your crime (Score:5, Insightful)
Police do pursue murders by computer forensics
The Boston Globe just had a section on how police aren't solving homicides very well.
the DEA doesn't spend an inordinate amount of time on "a few ounces of pot",
Yea, tell that to all the people pursued and convicted in CA after the medical marijuana law passed.
a history of violence against women is not a crime in itself,
no but "beating countless women" is.
some Islamic charities are known to support terrorism,
yes, but the vast majority of charities do not fund terrorism. Why not go after irish catholic charities? Some of those helped the IRA.
bilking millions of dollars is also not necessarily a crime
The term "bilk" absolutely describes fraud.
lastly the incident in San Francisco you referenced was not at all typical.
Yea? Well, how many cops do you know. You can find stories like this on a regular basis.
origin of urban myth (Score:5, Informative)
Re:origin of urban myth (Score:4, Informative)
Actually Gutmann updated his article by stating:
the methods that applied specifically to the older, lower-density technology don't apply any more. Conversely, with modern high-density drives, even if you've got 10KB of sensitive data on a drive and can't erase it with 100% certainty, the chances of an adversary being able to find the erased traces of that 10KB in 80GB of other erased traces are close to zero.
Further in his later epilogue regarding the referenced article, he doesn't dispute the fact that article says exactly what he's saying (i.e. "one pass is more than enough"), he disputes the technique they used by saying it's totally flawed.
So yeah, even Gutmann says not to bother, and a single pass erase is more than enough in today's high-density drives.
"Less successful than a coin toss"?? (Score:4, Insightful)
From the article:
A coin toss is usually referenced as the worst way to try and predict a 50:50 chance event. Disregarding all of the obvious problems (i.e. - that the bits on a hard disk do not have a 50:50 distribution (unless compressed or encrypted), and that a coin is not necessarily the most random thing, I'm still left with a puzzler
If his methods have less chance of prediction than a coin toss, all he has to do is add a "not" gate at the end of his prediction algorithm, and he'll have better chance than a coin toss.
To take this to an extreme, assuming random incoming data, a coin toss has 50% chance of a hit for the next bit. If you find a method that has a 0% chance of a hit, then just flip its output and you'll get a 100% chance of a hit. Lower chances than a coin toss actually mean a good prediction ability
Shachar
RoHS has fixed this problem for us. (Score:4, Interesting)
Re:RoHS has fixed this problem for us. (Score:5, Interesting)
I've worked in the electronics industry too. You might get tin whiskers if you use an immersion tin finish on the board and a tin solder for the assembly, but you don't need to do that to get a RoHS compliant product. There are immersion gold, immersion silver, and other leadfree solder finishes available. Modern leadfree solder alloys don't have the same kind of problems with tin whiskers as earlier ones. Reflow heating should be preformed as well. Effective conformal coating can also reduce the risk of whisker growth. Another issue is that many vendors lie or don't properly track how their components are made. Don't trust the sales people! Test your parts yourself to make sure that they comply with the specs that you ordered.
I support the adoption of RoHS in the USA because I've seen how corporations ignore the safety of their employees and customers with regard to hazardous materials such as lead. Strong democratic unions could be used to keep companies honest, but currently American unions tend to be too corrupt and weak to be able to change the industry.
*shakes his head* (Score:5, Interesting)
I can't help but sit here shaking my head in some disbelief at the comments I've read on this thread. Slashdotters are a technologically savvy community for the most part, and I lost track of the number of times that I saw something to the effect of "The government probably has means/software/tools/hacks to get your info."
Now, I've done extensive work *for* the government in the realm of computer forensics, which is as far as I'll elaborate, and the tools we use are commercially available. Were anyone so inclined, you could even attend or get notes on FBI or DoD taught digital forensics classes.
There's nothing wrong with some good old fashioned suspicion or conspiracy theory, but the *one* area that slashdotters should be mostly competent and knowledgeable on has more of those wild ideas than anywhere else.
DBAN, DBAN, DBAN (Score:3, Informative)
Pop in a DBAN cd, hit enter. You can tell the boss that you've performed a wipe that meets DoD specifications. There's no real time difference in doing one wipe, which doesn't meet DoD specs, or the three that DBAN does by default. Unless, of course, you are sitting there watching the percent complete go up. If you have free time to do that, how can I apply for your job?
For the google impaired, http://www.dban.org/
Did anybody RTFCA? (Score:4, Informative)
In the epilogue of http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html [auckland.ac.nz], Peter Gutmann basically calls the author of TFA a rtrd.
Apparently, he's confusing two different techniques, and Gutmann claims that, of course it won't work the way he's doing it. He's doing it wrong. You can't use the Magnetic Force Microscope to perform an error cancelling read, it doesn't work. The success rate is - surprise! - less than 1%, exactly like TFA claims.
Also, mentioned in Gutmann's epilogue, TFA confuses an MFM and a scanning electron microscope. They are not the same thing. An MFM reads magnectic levels, it doesn't "see" electrons like a SEL will.
In any case, Gutmann agrees with TFA but for very different reasons. The new encoding techniques nullify the MFM. There is no point using it because it won't give you any usefull information on a modern drive. Also, the extremely high densities mean the only practical and reliable method of recovery is basic error-cancelling techniques, and that's only practical after one wipe. Even then, it's iffy at best.
So yes, a single wipe is probably all you need. But who knows what data recovery techniques will be invented? A single pass is probably good enough right now, but 3-4 random passes is pretty much a sure thing, regardless of future techniques.
Re: (Score:3, Informative)
Why not:
dd if=/dev/random of=/dev/hda
instead?
That way you get random data, not just all zeros. Also you probably want /dev/hda so you blank the entire drive; not /dev/hda1 which only blanks the first partition.
Cheers,
Dave
Re:dd if=/dev/zero of=/dev/hda1 is enough for ever (Score:5, Informative)
That would take too long - you can't depend on the blocking kernel random generator, as it needs a source of data to keep feeding the entropy pool.
Re: (Score:3, Informative)
You want /dev/urandom. Pseudorandom data is plenty for this purpose, and it won't take forever to generate either.
Re: (Score:3, Informative)
Re:Tag this "itsatrap" (Score:5, Informative)
That'd probably be this challenge [16systems.com] from further up the page - $500 at the moment, and apparently three companies have turned it down after the dd command was mentioned because they 'know' it isn't possible.
Re: (Score:3, Insightful)
only $500? (Score:4, Insightful)
Re: (Score:3, Interesting)
That whole "reading between the tracks" thing hasn't been true since hard drive head actuators were powered by stepper motors (over 20 years ago). Voice coil head actuators are precise enough to eliminate this concern entirely.
Re:Just one layer of paint (Score:4, Funny)
I hear writing random numbers like 2s and 9s to the drive works REALLY well
Re: (Score:3, Insightful)
I've sent a drive in for data recovery before and was asked which operating system to recover: solaris or Windows NT....
A reinstall is not a drive wipe in regards to forensics. While IT may call it a wipe and refresh the data is easily recovered. It's this confusion between delete, reinstall, format, and wipe that starts unfounded rumors. Not to mention the differences between different file systems.
A wipe is a writing data to EVERY sector. A format does not wipe, a deletion does not wipe and wiping is not common practice. With the size of drives today, you'd practically have to leave it going overnight. Most drives go
Re:It makes sense, BUT... (Score:5, Informative)
> if you can recover from 1 overwrite, while still being able to get the new data, the
> capacity has just doubled.
Not if it takes hundreds of hours to do and recovers only 3/4 of the data on average. There is a lot of room between "not secure" and "reliable data storage".
It is very unlikely that any of us need worry that our overwritten files will be recovered, though. None of us have secrets that important.
Besides, the bot that controls your Windows box has already uploaded all your passwords.
Re: (Score:3, Insightful)
Nice theory, but totally full of shit.
I've done contracting for the government, and worked on a proposal which would have required "Secret" clearance for all staff involved. I have also worked with medical records for the local health authority. Finally, I've worked for oil companies that have both liability of both customer records and planned exploration/acquisition to keep private.
You're making the mistake that everyone else on /. is just like you, huddled at home, worried about their pr0n collection. Ho