It was time to get rid of a ten-year-old external hard drive that I used for backups. To make sure all the data was erased, mainly to protect things like passwords and credit card numbers, I explored the options available to me on my Mac Mini. The Disk Utility has several levels that can be used to wipe the data, so I elected to use the most secure, a seven-pass erase that writes random data seven times, just like the ultra-paranoid Pentagon would do. It took over a day to complete, but what the heck, the Mac didn't really have all the much to do anyway. You can explore options at the link below.