A DOD wipe (Department of Defense) is 7 passes of a format and zero writes to the entire HDD...
I would think they wouldn't take such measures without having just cause to protect sensitive data....
I'm quite sure they know alot more about computer forensics than the average User...
The DoD method is based on an out-dated and essentially debunked paper that was based around older recording methods, particularly those used in floppies. Modern Hard Drives work completely differently. Here is a quote from a (sorry for the length, this forum needs "spoiler" tags or something equivalent) paper on the subject.
The basis of this belief is a presupposition is that when a one (1) is written to disk the actual effect is closer to obtaining a 0.95 when a zero (0) is overwritten with one(1), and a 1.05 when one (1) is overwritten with one (1). Ths is false and in fact, there is a distribution based on the density plots that supports the contention that the differential in write patterns is too great to allow for the recovery of overwritten data. The argument arises from the statement that "each track contains an image of everything ever written to it, but that the contribution from each "layer" gets progressively smaller the further back it was made". This is a misunderstanding of the physics of drive functions and magneto-resonance. There is in fact no time component and the image is not layered. It is rather a density plot.This is of prime importance to forensic analysts and security personel. The time needed to run a single wipe of a hard drive is economically expensive. The requirements to have up to 35 wipes [12] of a hard drive before disposal become all the more costly when considering large organisations with tens of thousands of hosts. With a single wipe process taking up to a day to run per host through software and around an hour with dedicated equipment, the use of multiple wipes has created a situation where many organisations ignore the issue all together – resulting in data leaks and loss.
The inability to recover data forensically following a single wipe makes the use of data wiping more feasible. As forensic and information security professionals face these issues on a daily basis, the knowledge that a single wipe is sufficient to remove trace data and stop forensic recovery will remove a great deal of uncertainty from the industry and allow practitioners to focus on the real issues.
Because of the misconception, created by much older technologies (such as floppy drives) with far lower densities, many believe that the use of an electron microscope will allow for the recovery of forensically usable data. The fact is, with modern drives (even going as far back as 1990) that this entire process is mostly a guessing game that fails significantly when tested. Older technologies used a different method of reading and interpreting its than modern hard called peak detection. This method is satisfactory while the peaks in magnetic flux sufficiently exceed the background signal noise. With the increase in the write density of hard drives (Fig. 3), encoding schemes based on peak detection (such as Modified Frequency odulation or MFM) that are still used with floppy disks have been replaced in hard drive technologies. The encoding of hard disks is provided using PRML and EPRML encoding technologies that have allowed the write density on the hard disk to be increased by a full 30-40% over that granted by standard peak detection encoding.
Additionally, hard disk drives use zoned bit recording which differs from floppy drives and similar technologies. Older technologies (including floppy disks) used a single zone with a write density that is several orders of magnitude larger than that used with hard disks. We have not tested recovery from a floppy disk using these methods, but it would be expected that the recovery rate would be significantly greater than with respect of that of a hard disk platter - although still stochastically distributed.
The fact is many people believe that this is a physical impression in the drive that can belie the age of the impression. This misconception is commonly held as to the process used to measure the magnetic field strength. Using the MFM in Tapping Mode, we get a topography image that represents the physical surface of the drive platter. The magnetic flux density follows a function known as the hysteresis loop. The magnetic flux levels written to the hard drive platter vary in a stochastic manner with variations in the magnetic flux related to head positioning, temperature and random error. The surfaces of the drive platters can have differing temperatures at different points and may vary from the read/write head. This results in differences in the expansion and contraction rates across the drive platters. This differential can result in misalignments. Thermal recalibration is used on modern drives to minimize this variance, but this is still results in an analogue pattern of magnetic flux density. One of ways used to minimize the resultant error has come through the introduction of more advanced encoding schemes (such as PRML mentioned previously).
Rather than relying on differentiating the individual peaks at digital maxima,magnetic flux reversals are measured by hard drive heads and processed using an encoding process (PRML or EPRML) that is based on determining maximum likelihood for the flux value using a digital signal sampling process. Complex statistically based detection algorithms are employed to process the analog data stream as it is read the disk. This is the "partial response" component. This stochastic distribution of data not only varies on each read, but also over time and with temperature differentials. This issue has only grown as drive densities increase.
Basically, a single pass is enough. Though I firmly hold that if you need to securely delete anything you're either paranoid or a criminal, or an LY (Linux Youth). Possibly both. Why? Well, for one thing- the person who cares the most about your data is you. Not some random person out there in the wild. Nobody grabs used hard drives and goes "I think I'll use a recovery tool to try to reconstruct the data that used to be on this drive for my EVIL SCHEMES.". the second case speaks for itself, if your computer has illegal material on it, you're going to be paranoid that some random person rebuilding your data will find that illegal content and report you! The answer to this is to, well, not put the illegal content there to begin with. (pirated software btw is a common thing I see people cite "well I copied XYZ and I don't want to be reported". That's stupid. Nobody would waste their time to rebuild a disk structure just to find if the person before them used pirated software, and it's not really that easy to tell if they did anyway. That, and it's not strictly illegal depending on the actual action taken.
The third one comprises those bushy-tailed youngsters who, as leet haxxors, want to protect their stupid xchat scripts from being stolen, because MicroShaft is out to steal their ideas. So they of course will use a fully encrypted disk to store their data, under the false impression that they couldn't just have the password beaten out of them if they <really> wanted it. But nobody does, they just delude themselves. And usually, at least in my experience, encrypting your stuff just makes it harder for you to access.
In the Original Poster's case, I don't think it's important to wipe the drive at all, especially since it's purpose is to keep unscrupulous people from private data, since unscrupulous people
Already have that data. (and nobody would bother to rebuild a disk structure to find that data anyway).
