This is where I become confused: if overriting data with zeros (e.g. "Normal" file deletion) makes it irecoverable to begin with, why waste time and harddrive space passing over the deleted data several times over again with randomly generated data (e.g. "Secure" file deletion)?
Some people do have data recovery programs, & I know from testing them out, that there is a WIDE variance in what can & cannot be recovered. I have tested a utility that can recover deleted/corrupt partitions on a drive, as well as data from drives listed in RAW format, etc.
Although, it seems at present, that properly overwritten data is hard or almost impossible to recover. But I am a standard user.
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The Government has sophisticated machinery to use, such as Electron Microscopy drive imaging.
In addition, they also have machines to make an HDD read to the left or right side of a track just slightly, to pick up parts of an image that may have been slightly to the left or the right of the track that a drive is writing to. Think of it like a highway. A 3 lane one, where you are normally driving center, but every now & then, you like to pass someone in the left or the right lane. Same concept, just the data may be in the center of the track being written, or it may reside slightly to the left or the right of it.
And, I have also heard they have Magnetic Underscan tech, to try to make an image of the "Ghost" image that may be left on the underside of a track.
Then, you combine this with the fact that it has been said that certain goverment agencies do have the capability to read the drive with a specialized utility in order that they can determine, hey, if this is a 0 at this electron v level, then it must have been changed, & by using the volts level of the 0 & 1 beside that, determine what this track must have used to have been.
Some say they are able to go multiple levels deep with an advanced scanning algorithm. Hence, by overwriting a drive multiple times, you at least make them have to work that much harder to recover the data with such a utility. Frustrate them to the point they may decide it just isn't worth it, or even realize it is nearly impossible to recover, even WITH such utilities.
This isn't to mention that Windows marks sectors as bad when it is no longer able to read from them & if a guy can write a program like Spin Rite, then imagine what the government can do with specialized machines to mount your harddisk onto in order to read the data back, particularly in damaged/bad sector areas, as they would hold a treasure trove of data if successful.
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Given that the Government has much higher capabilities (& also $$$) than the normal user, it cannot be over-estimated what they are capable of. Would a standard user know about training a dog to search for a missing person? No! Nor would they know about finger printing techniques or how to do a number of other forensics related tasks involving capturing data from a machine via a specialize machine that images a drive via a hardware write blocker to prevent changes to the data they are recovering live.
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P.S. Why all the paranoia? Well, given that areas like China are prevented from accessing a lot of things considered by the Government as illegal, it helps people in China to rest more or lest at ease of mind, knowing they are able (hopefully) to overwrite the data on the drive enough times to prevent the recovery, even by the government, should they be after someone for whatever reason.
Oh, it isn't just users in China anymore. Look at the Homeland Security act.
You do the math, ![:)]()