Paranoia and deletion: the wipe man page

[sp332]

I'm sorry, but this info is nearly ten years out-of-date. First, the Gutmann method was designed for encodings back in the days of RLL/MFM encoded drives. For newer drives which really push the physics quite a lot further, two passes of random data are enough to throw the magnetic domains into a statistical dead heat. There just isn't any physical room on the drive to hold old data.

Secondly, new drives reserve a percentage of the room (invisible to the user), in case some of the sectors go bad the controller will re-map them transparently to new sectors. This might leave old data in the old sectors, where you can't normally see it but an investigator armed with the proper ATA commands can. (This isn't a conspiracy of the government and drive manufacturers, it's all there in the ATA spec.) The correct way to securely erase a drive is to send the drive the SECURITY-ERASE command. The drive controller will securely erase every part of the drive. https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase The NSA actually recommends this to other government agencies, so it's probably OK.

[jwr]

But how do you know if the data actually gets erased by the drive?

[Confusion]

Silly conspiracy theory.

1) The scope is too large. Too many engineers at hard drive manufacturing companies would have to know about it.

2) Too America-centric. Engineers in foreign countries, that actually build most of the stuff, would know about it. It would be an enormous security gap that they could use as well.

The sad thing is that such paranoid fantasies, that are easy to debunk, blind you to the actual conspiracies, that are less comprehensive, more subtle and therefore much more threatening. I bet the TLA government agencies love these stories.

[SoftwareMaven]

The invisible yellow dots identifying printers went a long time before becoming common knowledge. I don't believe TFA for an instance, but it doesn't seem an impossibility.

[rapind]

Maybe it's the gov who posits these theories?... nah.

[ck2]

I always dissemble my old hard drives, it's therapeutic somehow.

I am not sure how they broke that disc into so many pieces though, in my experience they are incredibly strong and rigid.

The discs make great wind chimes too.

Harbor Freight has a $3 security bit set if you have drives with special screws.

[hnhg]

Sorry to be a pedant, but I think you mean "disassemble" - I always get the two mixed up too.

[wazoox]

Some drives have glass platters AFAIK. This would explain how this one was broken.

[rasur]

My method for dealing with old drives:

- remove top plate of drive - a number of heavy blows with a Sledgehammer. - incineration.

This usually does the trick.

[InclinedPlane]

Liquid nitrogen?

[hexley]

Glass platters?

[Mithrandir]

The man page is correct about quite a few things, but it's also a bit sarcastic:

       The  best way to sanitize a storage medium is to subject it to tempera-
       tures exceeding 1500K.  As a cheap alternative, you might use  wipe  at
       your  own  risk.  Be  aware that it is very difficult to assess whether
       running wipe on a given file will actually wipe it -- it depends on  an
       awful  lot  of  factors,  such  as  :  the type of file system the file
       resides on (in particular, whether the file system is a journaling  one
       or not), the type of storage medium used, and the least significant bit
       of the phase of the moon.

But no matter what, wipe is a really great program.

[mmaunder]

I sleep at night knowing that the teams of highly effective government data recovery personnel that Hollywood portrays will never exist.

[troels]

    Of course this shifts the trust to the computing system,
    the CPU, and so on. I guess there are also "traps" in the
    CPU and, in fact, in every sufficiently advanced mass-
    marketed chip. Wealthy nations can find those. Therefore
    these are mainly used for criminal investigation and
    "control of public dissent".

I'm unsure in which way a government agency could benefit from having backdoors in the CPU? Even if they did, and even if it could detect that some sort of encryption was going on, where would it store the interesting data?

[sesqu]

Well, there was/is that trusted computing thing, i.e. putting DRM on the PC in hardware. The benefit would be denying encryption from terrorists/pirates/dissenters, like he just said. Interesting data can be stored just about anywhere, from phoning home to hidden partitions to having a small flash on the BIOS, depending on what's deemed interesting (logs, sector addresses, cryptographic keys, painted files).

[Jach]

Funny, I was just having a conversation today with a friend who works for the company selling http://www.whitecanyon.com/wipedrive-erase-hard-drive.php and remarking that it may keep your data safe from identity thieves, it wouldn't protect you from the FBI.

[MikeCapone]

Did he explain more specifically why he thinks it would "protect you from the FBI"?

[Entlin]

To everybody spending thought on this: Relax, nobody is interested in your porn collection.

[haribilalic]

I've used such tools to wipe my hard drives before selling or donating used computers (although I would use them before disposing of a hard drive in any way, really). I have heard of people buying up used computers and hard drives and extracting saved passwords from them.

A lot of people are smart enough to format it quickly, but not everyone will let (or know to) a computer sit for dozens of hours so that things might be wiped more securely.

[chanux]

Any idea what's the difference between wipe and shred?

[naner]

The shred man page warns you that the tool is not fully effective on journaled filesystems. I doubt wipe is, either.

[endian]

Does anyone know if any such FOSS works with SSDs and their wear-levelling of their writes?

[tedunangst]

wipe is rather unlikely to overwrite the bits on an SSD. Even with TRIM (which wipe won't use, btw), the disk will prefer using a blank sector to one it has to erase. Reading the currently unmapped spare sectors is probably something anyone with a solder gun can do.

[srean]

An alternative could be to overwrite the disk with null bytes.

  dd if=/dev/zero of=/dev/hda bs=1M

Wonder if it is going to be slower than wipe.

[ComputerGuru]

....multiple times.

Overwriting it once prevents software reconstruction of the data, but magnetic analysis of the underlying disk itself can reveal (depending on the voltage returned by the resulting 0 or 1) whether the previous value was (within a degree of certainty) a 0 or 1.

[Someone]

That is nsufficient to be 100% sure that all our data gets overwritten. The disk's firmware could discover that a block is unreliable and never write to it again. Such a block could contain recoverable data.

Also, I am not sure that this is guaranteed to overwrite the last part of a disk whose size is not a multiple of 1M. I guess that will depend on how eagerly the device detects ENOSPC conditions.

[hexley]

For those on Mac OS X (and perhaps *BSD?), we have srm.

The Secure Empty Trash function is a frontend for this IIRC.

[stcredzero]

I wish there was a version that only overwrite once with 1's. That would be best for my SSD. (Which has wear leveling and is formatted with a journalling filesystem anyhow, so perhaps it's moot.)

[coffeeaddicted]

But what to do against those brain-wave readers? I better start thinking encrypted!

[deutronium]

I love this section:

"I strongly recommend to call wipe directly on the corresponding block device with the appropriate options. However THIS IS AN EXTREMELY DANGEROUS THING TO DO. Be sure to be sober."

[suraj]

How would a hard disk controller detect encrypted data? It is essentially a (psudo-) random stream of bytes. Even if the controller is programmed to recognize such streams, it would be easy to first wipe disk by writing small random files all over and then wiping with 0/1 pattern. So any cached data is essentially worthless.

[cloudwalking]

When I was younger, I erased a harddrive by covering it with burning thermite. It was pretty impressive, melting the drive, turning the sand underneath to glass, and burning through the asbestos pad into the cement.

[ams6110]

I use DBAN to wipe hard drives before disposal. If you are replacing a failed drive, the only reasonable thing you can do is physically destroy the platters.