Yeah, Mangetout. Fl4merZ r0xx0r! Fl4merz p0wnZZ j00! Fl4merZ 3ng4g3 1nn d33-v33-4nt sh1zzn0tch w1t y0 m4t3rn4l pr0v1d3r!
D0nt’ h8 d4 fl4m3r, h8 d4 fl4m3!
Now for some beats I know ya hep cats are gonna groove on.
Overwriting data with more data isn’t fully secure: All magnetic media preserve `echoes’ of what was once written to them, so a determined enough cracker with sensitive equipment could read stuff off of partitions you’d overwritten with random data (no, the digits of pi aren’t good enough because they’re too well known and can be produced cheaply with a purely deterministic method (ie, a computer program)).
Even if you are willing to risk that, beware of virtual memory and journalling file systems. Both of those things use the drive for something other than simple, linear, long-term storage (if I understand journalling file systems correctly, which I might not). This means that your data could end up anywhere on the disk and be impossible to see with conventional methods. Taking a hex editor to a raw disk image isn’t the most amusing way to spend a Friday night, but you can be pretty sure you’ve erased the sensitive data (assuming you know what it looks like in hex and plain ASCII).
If your privacy is worth more to you than the price of the drive, burn the thing. Take a sledghammer to the remains. Take it to a shooting range and fire hollowpoint rounds at it from high-powered rifles. Put what’s left in a box and toss it in the East River at midnight to sleep with Jimmy Hoffa and JFK’s brain, preferably while wearing a pentacle and chanting the Requiem Mass backwards. In other words, be the kind of destructive maniac head crashes and bizarre memory errors have driven you to be. Be a hacker with a hacksaw.