PCFormat Forum Archive

Hi Folks
One thing I cannot understand. How can data still be retrievable after formatting a HDD? From what I understood, the head passes over every part of the drive and changed the magnetic properties of the underlying disk. As the data is in these magnetic patterns, how can it survive? How does it help to format the drive a few times?

Can someone provide me with a link to how it works?
Thanks!

Because it's a high-level format, so it only wipes the file system. The data isn't physically gone, it's just not registered in the FAT.

Psych0_Cr1tt3r wrote:Because it's a high-level format, so it only wipes the file system. The data isn't physically gone, it's just not registered in the FAT.

Yip, what he said. You're only removing the reference to the file, not the file itself.

There are many, many programs that will erase the information on your hard drive comprehensively.

http://en.wikipedia.org/wiki/Disk_forma ... atted_disk

Use wikipedia and be cool!

BUt then how come it takes ages to format a large drive. If the reference is only removed in the FAT, it should be very quick...or am I missing something?

Depends on what kind of format and with what you are formatting. A quick NTFS format in the Windows XP setup is most zippy. A full NTFS format wipes the file system and runs one of those half-bottom scan disks at the same time, if I remember correctly.

Rikkelz wrote:You're only removing the reference to the file, not the file itself.

this relates only to a high level , (quick), format... a full format is technically a low-level format, switching the bits back to 0 position... the confusion here is imagining that the bits relate to neat physical switches which, when set, retain no memory about previous positions.. this is not entirely accurate..

the physcial medium used to represent the bits *does* retain memory, to a degree, allowing low-level apps and mechanisms designed for the task to "reverse" the formatting.

for this reason, a securely formatted disc is one which has had every sector overwritten in a random manner, repeatedly... (the randomness is a requirement... if a repeating pattern is used the process could be reversed by running the pattern in reverse... and it needs to be repeated a number of times to ensure that the targeted sector is in fact being scrubbed, if we recall that platters spin in circles, so the head may not be aligned to the sector you're targeting). this makes it difficult to extract sufficient groups of historic bits to re-assemble the original data... the process, however, is extremely slow...

a more secure, and far less time consuming, method would be to subject the entire drive to a sustained magnetic field for a few minutes.. this is gaurenteed to re-align every single part of every platter... effectively scrubbing anything that was there before.. permanently... leaving you with absolutely pristine platters...

If I were to take a BIG magnet and take a HDD and lay the magnet over the HDD and move it around and around the HDD would it be clean and would the stuff still be recoverable?

PsyCLown wrote:would it be clean and would the stuff still be recoverable?

the platters would be clean, but the drive would probably require repair before they could be used again.... if the platters aren't damaged in the process...

What do you have on your system that you want off it so badly? The best security is Raid 0 and you change the order of the disks before the format. Unfortunately requires more than one HDD.

Regards

Nothing .. at least at the moment ... but I could not understand why it was possible to recover data from a formatted drive.

Ive alway wondered.

Or thought of making an application that would corrupt a file badly by pumping junk into it or even delete the contents then just delete it.

Wouldn't that be the ultimate way to destroying a file?

if you look at last months custom PC they gave a little guide to creating a bat file that not only deletes all the files of a folder but also writes 0's to that portion of the hdd. that shouold render all info gone

Just find some application that'll do it for you, if yo want to erase data securely that is. I think it was a Symantec App that I used to use that had something like this, you could even set how many times it overwrote the file with random data.

Something I've been wondering also on this topic. I once read about a hacker, might have just been a story, that installed electromagnets on the side of the doorway to the room where his computer was kept. I'm guessing these were usually off and then he'd push a button if the cops suddenly showed up and as they carried his PC out the room the HDDs would be wiped. I'm actually pretty sure that I also read in somewhere that the procedure when a computer is confiscated says to check for magnets and things like that that could corrupt data on the system.

My question is, how well would that work? Would it be effective in making sure there is nothing on the drive/s?

SBSP wrote:Ive alway wondered.

Or thought of making an application that would corrupt a file badly by pumping junk into it or even delete the contents then just delete it.

Wouldn't that be the ultimate way to destroying a file?

Nope because some files will have virus protections and some will just give errors....

The best way to "format" a HDD is to download a program that writes over data a few times......this program takes about 12 to 24 hours to completely wipe a HDD clean can't remember the program's name but they not all that exspensive around $10 to $20

KillerByte wrote:that shouold render all info gone

no...

the physical medium is *not* like a collection of switches. by analyzing the disc surface you can make an educated/calculated guess about the last few bytes stored in a particular position. you *can* roll those nulls back. Especially if the entire sector is ALL nulls... that just makes it easier. this is, after all, what a "full format" does...

for this reason you would be more succesful in permanent deletion by writing multiple bursts of random data over the sectors being wiped. this junk data effectively reduces the chances of any rollback.

@Azgard: yess... depends on the magnet used, and would also result in physical damage to the drive... you would, however, have to mask the noise... and not mind the cancer risks

azgard - I see you watch SG1

the cops can't take your PC without a warrant and if you have done something illegal then put your microwave by your PC, if the cops pitch up throw your HDD int he microwave and turn it on. goodbye data.

Azgard wrote:Just find some application that'll do it for you, if yo want to erase data securely that is. I think it was a Symantec App that I used to use that had something like this, you could even set how many times it overwrote the file with random data.

Something I've been wondering also on this topic. I once read about a hacker, might have just been a story, that installed electromagnets on the side of the doorway to the room where his computer was kept. I'm guessing these were usually off and then he'd push a button if the cops suddenly showed up and as they carried his PC out the room the HDDs would be wiped. I'm actually pretty sure that I also read in somewhere that the procedure when a computer is confiscated says to check for magnets and things like that that could corrupt data on the system.

My question is, how well would that work? Would it be effective in making sure there is nothing on the drive/s?

There is a easier way but by no means the cheapest way is a HDD that has build in acid protection...was in the pcformat a while back

rustypup wrote:@Azgard: yess... depends on the magnet used, and would also result in physical damage to the drive... you would, however, have to mask the noise... and not mind the cancer risks Laughing

Well for the purpose I mentioned physical damage would be fine Do electromagnets make a lot of noise?

KillerByte wrote:azgard - I see you watch SG1

the cops can't take your PC without a warrant and if you have done something illegal then put your microwave by your PC, if the cops pitch up throw your HDD int he microwave and turn it on. goodbye data.

Yea I do watch SG-1.. lol

True, but then I'd have to keep a microwave in my room. Could always just take apart a microwave, put the magnetron inside your case and have a little switch to turn it on. Just make sure it's shaped so that the EM waves don't go anywhere near you. That would destroy everything in your case though. Huge enduced emfs and currents and such

KillerByte wrote:if the cops pitch up throw your HDD int he microwave and turn it on. goodbye data.

you would say goodbye microwave loooong before you had effected any damage to the platters....

the correct approach is something like Eraser, (goggle it), which can be scheduled to run during downtime basically overwriting unused space with tripe...

don't believe holliwood... ever..

what do you guys gotta hide to have it permanently deleted, your old porno collection etc