Originally posted by XavierP
As a side note - the NSA recommend wiping and overwriting 7 times. I believe that you have to do this for the NSA to consider it unrecoverable.
No, the NSA does *not* say that wiping 7 times with pseudorandom data will render it unrecoverable. In fact, the NSA physically destroys HDDs with any type of sensitive data on it. Only HDDs that have no sensitive data on them are wiped via software. That's where that spec you quoted came from.
Also, due to the nature of magnetic media, it is nearly impossible to render all data unrecoverable even if you wipe 35 times. It's a huge misconception among people. The FBI doesn't use software to recover data (most of the time). They literally take the HDD apart and analyze the platter directly. And due to the density of drives today, data will almost always remain on the platter.
But if you have nothing incriminating on the drive, then you have nothing to worry about. No one would go to all of that trouble just to steal your social security or credit card number.
Also, make double sure that your swap partition was also wiped in the process. That's the first place forensics experts look. If you are super paranoid, there are utilities out there (like the one that comes with Eraser - google for it) that does a low level wipe. This is a much better way to overwrite data than running one from the OS level.