Data Mining Used Hard Drives

linuxwrangler writes "One hopes the /. crowd knows the perils of discarding storage with sensitive data but this article drives home the point. Two MIT grad students bought used drives from eBay and secondhand computer stores. Among the data found on the 158 drives were 5,000 credit-card numbers, porn, love-letters and medical information."

Comments

Data worth more than the computer

[blamanj]

It's long been know that laptop theives are often more interested in the data than the computer.

Some computers sold on eBay are sold for the data.

I can relate

[l33t-gu3lph1t3]

Picked 6 or 7 old 4gig HDDs from my father's company a few years ago, found their company credit line information, personal (and some very erotic) email, and a surprisingly large collection of nudie photoshopped Gillian Anderson photos. Oh yeah, and like 100 different (and I must say, very well-done) quake2 "crackwhore" models and skins lol. I love the people who don't clear their HDDs, it's like treasure chests, you never know what you're gonna get.

Not so bad.

[Annatar2]

Thats not so bad. My dad happens to be a garbage man and often brings along an occasional system he's scavanged from the dumpsters along his route. Currently I have in my possession an old IBM Aptiva with some guys bank account information on it (He did his checking and stuff with it apparently), but worst of all I have what appears to be an old Gateway tower used to store Medical information for a major hospital in the area my father works. I have over 2 gigs of peoples medical history, including what they were put in the hospital for, insurance information, release dates ect.

I should really do the honost thing and reformat it but its always fun to flip the thing on and just page through stuff.

Re:HD Abuse

[davidc]

Take 'em apart and use the magnets as fridge magnets. They hold up an enormous amount of paper, although they do tend to nip one's fingers occasionally :)

It's not just hard drives

[b1t r0t]

A few years back I found some backup cartridge tapes (the big 4x6 kind) and a couple of tape drives at a Goodwill store. While there wasn't anything particularly useful on it, I could tell that it was the shell account machine used by half a dozen or so Ingres developers.

No database code or data, just typical home directories and stuff. And they were running SCO, but boot blocks and stuff don't generally get written to tapes, so no chance of warezzing from it.

I also snag SCSI hard drives and SyQuest cartridges when they show up for five bucks or less at thrift stores, since most of that is Mac stuff and I'm a Mac-head.

Once I got a 6100 at a thrift store. I presume the owner stopped using it when the PRAM battery died. (When a 6100's PRAM battery dies, the video settings go with it, and unless you're using a fixed-frequency monitor, you get no video unless you hold down command-option-P-R. Looks like real bad a hardware problem when it's just the battery.) I could tell it was used by some college guy, studying to be a lawyer, I think.

"Thrift store hard drives are like a box of chocolates... you never know what you'll find!"

this is also a problem for warranty.

[Unknown Poltroon]

I have had 2 drives fail well within the warranty period, and did not return them for just this reason.

Random Bit Overwrite

[akamoe]

US DoD Spec: 3 passes
German DoD Spec: 7 passes

(from http://www.ontrack.com/library/dataeraser.pdf)

-- R

Re:DPA

[tealover]

I remember working on my very first IBM pc. My girlfriend's mother was dating a guy and he gave her an old 8086 computer (this was back in '94 or thereabouts). Well, I started playing with the computer. He had an early version of Norton Utilities on it. I played with the undelete file utility and found that there were lots of deleted files. I recovered some of them and started to read them. Most were boring. One wasn't

This guy wrote about my g/f's mom about how he was banging her for the last 15 years. She had only been widowed for 10 years. He also complained about how she only came around when she needed money and how he was tired of banging her wrinkly ass.

Also, this guy was a principal at an elementary school. He was apparently fucking several women at the school, even getting blowjobs at work!

I was simply amazed. My g/f didn't even really know that this guy was dating her mom (some women are so stupid). She just thought he was a family friend. I couldn't tell her about what I found because I knew she would have been really upset.

I learned from that day on that simply deleting a file was not going to hide anything. I'm actually holding onto a defective laptop thathas been broken for months. I don't want to toss it out until I can either recover the harddrive data myself or until I can safely dispose of the harddrive.

A story of DISK, SRAM and DRAM data recovery

[tagman2]

Summary of the long posting below:

• Data from a hard disk that as been wiped multiple times can be recovered.
• Data left in SRAM and DRAM for a long period of time can be recovered even though the system has been powered off for a while and the SRAM has been cleared.
• While it is hard to recover wiped and old data, it is not impossible.

First, a little background:

I belong to a group that polls/tracks certain elections around the world. In one recent election, there were a number of claims of voting irregularities. Our group became part of a post-election analysis team to look into these irregularities.

We were able to determine that one desktop system in particular contained some critical raw voting data (raw precinct counts of per ballot slot data). The election officials were more than reluctant to give us a copy of that raw data. By the time we were granted a order requiring the election officials to let us access the data, someone had attempted to throughly wipe the desktop system of all traces of data.

We thought we had lost that critical data. But thanks to a chain of contacts we were referred to a consultant that specializes in extremely difficult data recovery. After checking some references (and obtaining more money from OUR client: the consultant was VERY expensive), we hired this consultant.

Much to the surprise of the election officials we obtained an order that allowed us to physically take possession of the system. The system was turned over to the consultant who recovered enough critical election data for our needs.

The recovery included data from the wiped system hard drive as well as from SRAM and DRAM.

Regarding disk recovery:

The disk drive had been wiped by a utility that, we presume, had been run from a CDROM. The wipe tool wrote over the entire disk 35 times, 8 of them were random and 27 of them were fixed patterns of 3 bytes each.

Not all disk data was recovered. Part of the reason was that the data recovery method was not 100% perfect. Part of the reason that some data was not recovered was a simple matter of time. (The consultant was in between two already committed projects and only had a limited amount of time to work for us.)

The consultant did recover some deleted files that were critical to our work. Not everything was recovered, however. Parts of the swap/VM-paging area that might have contained some useful data were not recovered. Also some disk data critical to file and directory layout was not recovered making recovery of parts of the file system layout difficult to map.

Still, some important files (a spreadsheet, simple database file, browser cache, some EMail, etc.) were recovered even though the drive had been wiped 35 times!

Regarding SRAM recovery:

n3rd posted a comment asking about recovering data from RAM.

There are methods that can recover RAM data. Both SRAM and DRAM can be recovered.

According to the consultant, the storage of the same data in SRAM over a long period of time has the effect of altering the preferred power-up state. They said that SRAM can ''remember'' data for days after it held it for a long period of time. This memory can be determined by a ''partial powerup'' (I presume they mean a lower than normal voltage?) and then going ''full on'' and reading the initial values of memory.

In the case described above, the SRAM had been deliberately cleared prior to our group taking possession of the system. The consultant was able to recover the original data even though the SRAM had been cleared and the system has been powered off for more than a day. A simple clearing of memory was not enough to wipe out the long held memory effect.

Regarding DRAM recovery:

DRAM data was also recovered. Data left in DRAM for a long period of time can leave an ''impression'' thru a process somewhat different from SRAM.

As explained by the consultant: With DRAM, recovery comes not from detecting any left over charge, but rather detecting the stress (or lack of stress) from the thin oxide of the cells storage capacitor dielectric. The effect of this stress can be measured by using the DRAM self-test feature. In self-test mode, a small voltage is applied to a cell in order to measure its margin for error. The self-test margin is increased or decreased by the amount of oxide stress.

Not all of the DRAM memory was recovered. However certain critical portions of the DRAM held values for long enough period of time that data was recovered, even though the system has been powered off for more than a day. Data recovered included memory associated with a browser and a spreadsheet. Even though both the browser and the spreadsheet were closed prior to the system being wiped, they were left running long enough to leave behind their DRAM oxide stress.

Based in part on the recovered data, we concluded that candidate A was declared the winner due to a ''mistake'' in mapping ballot slot numbers to candidates. In some cases the slots for candidate A and B were reversed.

An incorrect vote count was reported by the election officials. It is our guess that when we came around asking for the raw data, someone began to collect it. At some point some official(s) discovered the blunder. The system was left on while they stalled for time. When it was clear that we were going to force them to turn over the data someone wiped the system and shut it down.

BTW: The majority of the election officials involved were supporters of candidate B. Even though their blunder caused them to declare candidate A the winner, they still tried to coverup their mistake.

Our conclusion was that the attempt to coverup the mistake was motivated by not wanting to admit the major blunder instead of because of candidate A's influence. This conclusion was reached in part because of messages that we recovered on another system that was not wiped. However we would have never been able to find that other system, nor would we have been able to match the raw slot numbers with the reported vote counts by candidate name without the help of the data recovery consultant and the critical data that they recovered.

I'll offer a few observations:

• Volatile data such as SRAM and DRAM is not as volatile as you might think.
• With enough will, skill and effort, old data can be recovered from a disk that has been overwritten multiple times.
• Packages such as PGP file wipe, GNU shred or Boot and Nuke are likely to only make it harder, but not impossible to recover the data.
• To quote from a paper by Peter Gutmann:

  '' Data which is overwritten an arbitrarily large number of times can still be recovered provided that the new data isn't written to the same location as the original data (for magnetic media), or that the recovery attempt is carried out fairly soon after the new data was written (for RAM). For this reason it is effectively impossible to sanitise storage locations by simple (sic) overwriting them, no matter how many overwrite passes are made or what data patterns are written.''

  And even though in that paper next says:

  '' However by using the relatively simple methods presented in this paper the task of an attacker can be made significantly more difficult, if not prohibitively expensive.''

  For our consultant, the recovery process was hard but not extremely difficult. It was expensive for us, however. :-( But we were happy to pay to have it done. :-)
• Whoever wrote the 35-pass disk wipe tool must have read that paper, or one similar to it because the overwrite patterns looked similar to the recommended list.

P.S. I know that some people doubt that one can obtain old data from SRAM and DRAM after poweroff. I did too until it was done for our group. To those who still doubt this: I will refer you to Peter Gutmann's paper on Secure Deletion of Data from Magnetic and Solid-State Memory for another source on data recovery methods.