So I can throw this in the woodchipper?
Personally, I think the OP’s needs will be met with a format and reinstall of the OS. If she’s really paranoid, get something like Eraser and overwrite the desired data at least 9 times.
Peace of mind: priceless.
Well, an update. Unfortunately, when I booted up my computer with the system recovery disk, it gave me an error message. From there, I couldn’t get the computer to boot up to the desktop. I took it to Pro-Byte because they would look at it for free. The young man there asked if I had installed a different Windows on the computer, which I had (XP). Then he said something about partitions and whatnot. They will charge me $60 to fix it. They also have a clearance on used Dells for $79. I’m considering my options.
On one hand, my HP was new in 2000. I’m a single mom, and I just bought a home. Every penny I have is budgeted; in fact, I’m getting a part-time job in addition to my teaching job just so I can build up some savings in case of emergency. I really cannot justify spending that money on my computer. However, I use my computer every day, and while it isn’t IMPERATIVE, it is very important to me.
Back to the thinking box.
Thanks for all your help 
I don’t mean simply “deleting files” … what I should have asked is whether or not data is recoverable from:
a) a REFORMATTED hard drive, or
b) a hard drive purposefully abused with strong magnets (like from the inside of a microwave oven).
The first few posts in this thread seemed to imply that any data could be recovered from any reformatted/heavily-damaged hard disk, anywhere, anytime. I didn’t think the hardcore recovery services were quite that good … though I knew plain ol’ deleted filed were easy to recover (Symantec/Norton even had a product for this circa 1999 … they probably still sell it).
:dubious:
C’mon … it’s only magnets, when you boil it down. Why wouldn’t turning all the magnets back into one directions (all 0s or all 1s) suffice?
OK … I’ve read through the thread fully now and data recovery services are about 10,000 times more capable than I thought they were :eek:
I thought that a hard drive was just so many mini-magnets … but clearly, there’s more than that going on.
We shoot ours. 7.62x39 FMJ does a good job on those platters.
The preferred method here is a disk sander.
ShredIt from Mireth technologies (www.mireth.com) costs 19.95. It allows you to wipe (write repeated zeros multiple times) to all areas of the HD not in use, so you can leave the OS and applications installed, but be sure that your deleted files will be virtually impossible to recover. It also has a complete wipe option. The license agreement allows you to install it on a PC, do the wipe and uninstall, to use on your next PC, which is better than the wipe products that are boot and 1 use only.
What’s the straight dope here? According to what cbarnes wrote above … even after using ShredIt, it’s relatively trivial to recover whatever files one may wish to.
(Honestly … this whole topic has thrown me for a loop. I knew a simple DELETE wasn’t sufficient, but always “knew” that a disk reformat was the total answer to this problem)
Hey … wait a minute – do hard drives have infinite ability to record data (or close to infinite)? What I mean by that is: are there ways to take advantage of HD material’s “permanence of information” … so that a 100 G HD could store what is actually a terabyte of data.
And if the above is NOT true … how is everything and anything recoverable? Is cbarnes overstating his case? Is there, in fact, considerable difficulty with recovering files off of disks wiped in a very careful, deliberate manner?
This is really bizzare to wrap my head around … take a given sector on the HD. Just how many files could be stored simultaneously on the same sector? And at the block level – is a single block able to simultaneously encode a 1 and a 0? If so, how?
The problem is that there is no standard definition of “formatting a disk”. It can mean anything from initializing the directory on a disk to doing a low-level format. In many cases, formatting the disk does not overwrite all of the old data, it just writes a new directory onto the disk.
Magnetic disks are fundamentally analog devices, like magnetic tape. If you measured the voltage on the reproduce head, you would see that overwriting or erasing a block is imperfect, like erasing pencil marks on paper with a cheap eraser. The old signal is still there, just substantially attenuated. The same thing happens with analog audio magnetic tape. If you record over your Backstreet Boys tapes with the Screaming Penguins, you can often hear faint traces of the Backstreet Boys during quiet passages in the Screaming Penguins album. With digital signals, like on a hard disk, it is often possible to separate the latest recording from the previous recording. Let’s say that we record the bits 10101010 on a blank disk. Reading the disk, we see +10 mV, -10 mV, +10 mV, -10 mV, +10 mV, -10 mV, +10 mV, -10 mV. Next, we overwrite those bits with 00000000. Reading the disk, we see -8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV. The disk drive considers anything greater than 0 mV to be a 1 and anything less than 0 mV to be a 0, so it reads that as 00000000. If we replaced the disk drive’s electronics with our own, we could see the raw analog signal. We could see that 10101010 had been overwritten with 00000000. Another trick is to look at the edges of the magnetic tracks on the disk. Traces of old data can often be found at the outside margins of the track, due to imperfect positioning of the recording head and incomplete erasure of old data.
For a better explanation, read Secure Deletion of Data from Magnetic and Solid-State Memory, Peter Gutmann.
Wow. Thanks for the informative post, mks57.
Question – are things different with thumb drives (which I understand are essentially little chunks ‘o’ RAM)?
They are chunks of FLASH not ram. In general most of the stuff that has been said about disks goes for flash. Deleting things means changing the diretory entry to say that the space is now available for new files. It is a lot harder to measure the trapped charge (which is how the data is stored) independently of the controling logic so trying to read what data has been overwritten is much more expensive and perhaps mostly impossible.
Just to clarify things the analysis that mks57 talks about is also expensive. You can send off hard drives to data recovery outfits which will use techniques like mks57 talks about but they are expensive on the order of $10,000 or more per drive. And they also may not have good success getting the data back.
This is really a question of what your data is worth and what you can reasonably expect a person looking for your data to pay to find it.
http://www.pcworld.com/howto/article/0,aid,110338,00.asp
According to this article, 3 writes of random characters x 7 times and even sophisticated “data recovery machines” cannot recover the data.
Writing 1x will defeat anyone trying to read the data w/o additional hardware, I’d expect. How would they get to the data “underneath” if that were not the case?
This makes intuitive sense. Look at the second half of mk57’s post above.
Now consider: after several re-writes, the recovery software must get to a point where it’s essentially being ask to blindly guess just how the following blocks:
-8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV, -8 mV, -10mV
… got that way. Surely the software couldn’t get away with just assuming that there was nothing more than a write, then a “soft” delete, and another write – the possibility that the same blocks have been overwritten dozens of time would always be present.
Ergo, cbarnes overstated his case wildly on pg 1 of this thread … although had he qualified his statement with “on the average user’s home computer”, he’s probably correct close to 100%. But for someone sufficiently motivated to really “wipe” a hard drive and willing to invest in the proper software … data recovery can apparently be made virtually impossible.
If you’re really paranoid, or have extremely sensitive data on the drive, physical destruction of the drive is the only acceptable method. Modern drives will silently replace weak or failing blocks on the disk with replacements from a set of spare blocks. This means that even if thoroughly wiped, there may be sizable chunks of data stored in parts of the disk marked as bad. The ease of accessing this data varies among drives, but it is on the disk. That’s why the government is a big fan of sledge hammers and grinders when it comes to disposing of disk drives that have been used to store classified information.
This was my thought.
“Pull”
“BLAM”
First, remove the hard drive from the computer and coat with a layer of Cramp’s Easy Bake Spread.
Preheat an oven to 400 degrees F.
Core an apple, and fill the core with brown sugar.
Take 8 pieces of Lebanon bologna and coat with Cramp’s Easy Bake Spread. Roll the bologna slices and fix with toothpicks.
Take a baking dish and add one litre of Fresca soda, and one 24 oz. box of Kellogg’s Sugar Frosted Flakes. Mix gently.
Add the HDD and bologna rolls, and top with the sugar filled apple.
Bake at 400 degrees for 6-7 hours, until incinerated.
Allow to cool, and then discard.
For those Windows users that are command-line savy, I always recommend this freeware tool, sdelete. It “implements the Department of Defense clearing and sanitizing standard DOD 5220.22-M”, allows you to specify the number of passes, and optionally cleans blank space. It is a single executable, so just stick it in your path and run ‘sdelete’ instead of ‘del’.
How do I completely delete everything from my computer in one fell swoop?
Geta copy of “Disk Manager” from the HD mfgr. It will reformat the HD completely.
ALso may be able to overwrite the HD with 1’s and 0’s to minimize the remote possibility of anyone retrieving any old data in the future.
Depending on the OS you may have to do a workaround or two.