>>179437
>>179438
>>179440
>One pass with just 0's? An undergrad could recover this shit in his sleep.
Prove it.
Shredders overwrite your files with random data several times before deleting them, but this has a drawback: Overwriting a file does not guarantee that it remains physically at the same location, in fact some filesystems guarantee that it will not.
The defragger from Microsoft will overwrite many unallocated blocks, but there is no guarantee it will overwrite all of them.
The important question is: Do you want to wipe a couple of files, or the entire disk? In the latter case, low level formatting used to work on older discs, but not on more recent ones. Nowadays you have to write junk all over the disc, then format it. If you want just a few files to disappear, there are apps for that, but I wouldn't trust them except with a FAT file system on a magnetic disc. If you know one that you know operates directly on disc, bypassing the operating system (you need root for that), then sure, use that.