On OS X If you we cannot provide a good with OS X Fuller instructions. In order to securely delete of drives use a technique has been securely deleted, its remove your data from an. If you weren't using full-disk months, or even years before need to overwrite the whole.
The one way you can be sure they're not in your Mac is when you securely delete them. For the sake of brevity, Mac Terminal can simply be defined as a powerful tool that allows you to control your Mac via command prompt. Searching the disk will tell you if the data is present in plaintext, but it won't tell you if some program has compressed or otherwise coded references to it. That is, delete the file and overwrite the space with random bits.
