Please note that file wiping makes sense only for HDD devices. See the File Erasure on SSD and HDD devices page for more details.
Wipe files before deleting: Select this option if you want R-Wipe & Clean for Mac wipe files before deleting to make their recovery impossible. This increases security, but also increases cleaning time. If the files are only deleted without wiping, they may be later recovered using any file unerase or recover utility.
If this preference is selected, the word Delete on various buttons changes to Wipe .
Currently R-Wipe & Clean for Mac supports 5 wiping algorithms:
What algorithm is to choose, depends on your specific needs. All of these wiping algorithms make recovery of wiped data with any software-based data recover utility impossible. So if you want to protect your information from a casual snooper, you may safely choose either the Zeroes or Pseudo-random numbers algorithm. The latter also conceals the fact that you wiped the data.
If you want more security, you need to know the following:
There are some techniques for recovery of wiped data. These techniques are based on the fact that magnetic medium on the hard drive's platters "store" some information about previously written data. Such information cannot be completely removed. Wiped data may be recovered even from mechanically damaged platters. So the only safe way to completely remove data from a hard drive is to mechanically grind the magnetic medium off the drive platters or dissolve them in special chemical solvents.
But in order to recover the wiped data using one of these techniques, a hard drive must be disassembled, its platters placed in a precise magnetic field measurement system, and the results of such measurement statistically processed. All that is very expensive and requires a very qualified and experienced personnel and a specially developed equipment. Only a very advanced organization such as a law enforcement or intelligence agency of a developed nation, or a special high-tech firm can afford this. Moreover, each successive wiping pass makes such data recovery much and much harder. So, the DoD 5220.22-M(3) clearing and sanitizing standard overwriting the data with a special pattern through 3 passes is a rather reliable and safe choice for this case.
If you need the ultimate security, use the DoD 5220.22-M(7) clearing and sanitizing standard, or even the Peter Gutmann (35) wiping algorithm. They render data almost unrecoverable, but they are extremely slow.