Secure Disk Erase

Recently I needed to clear off some old PC hard drives, so I went searching for a useful disk wiping utility. In the past I've used Norton Utilities, but that was an old DOS app which wouldn't be useful for today's larger drives, especially those with FAT32 or NTFS partitions.

This is a funny category to search for because you'll get tons of hits for a term like “secure disk erase”, most of which are not free and tend to be Windows apps that need to be installed. Instead, I'm looking for a command-line tool so I can run it from a boot disk, for example.

I eventually found two tools that work really well in two different situations:

  • For erasing files, I'm using SDelete from Sysinternals. SDelete can securely erase individual files, folders of files, or the unused free space on a volume. Source code is provided. Just as with all Sysinternals utilities, the SDelete product page has a good explanation of how it works and includes source code.
  • For erasing entire disks, I'm using Darik's Boot and Nuke (DBAN). This utility is small and self-contained, fitting on either a boot floppy or CD. To use DBAN, you simply boot it up, choose a couple of options, and it's on its way. By default it will make several write passes, taking an hour or more depending on drive size. The drive partition table is also erased, making way for a clean OS installation.

The combination of these two tools is a useful addition to your bag of PC tricks. DBAN is particularly useful for cleaning off a PC before you give it to someone else. It would be ideal for companies wanting to clean off old PCs before tossing or recycling them.

Update 2007-01-22: Fixed link to Sysinternals now that they are part of Microsoft.