Macs have 3 options in the OS for "removing" unwanted files :
- Empty Trash command (standard) simply removes the file's entry in the hard-disk index and the contents can be recovered fairly easily
- Semi-secure Empty Trash command (optional) does as 1 above and also writes random bits over the physical area the file occupied using 7 passes and flags the area as free, meaning it can be over-written immediately with another file. The contents of the original may still be recoverable, with some difficulty and with the use of software.
- Secure Empty Trash command (optional) does as 1 and 2 above and also writes random bits over the physical area the file occupied using an additional 28 passes and flags the area as free, meaning it can be over-written immediately with another file. The contents of the original are generally not recoverable without using special software.
Options 2 & 3 can take considerable time and system resources but may be useful for low-capacity removable storage e.g. USB pens, memory-cards, etc