Is it necessary to run a utility to securely erase a file that has been emptied from trash in Mac OS? or is the file erased completely when the trash bin has been emptied?
Since it is part of the Empty Trash function, it only works on items that are in the Trash when the command is executed.
To erase the free space on the disk, use Disk Utility's "Erase Free Space" button under the "Erase" tab. This zeroes out all of the free space, which is where previously deleted Trash items would be.
Disk Utility is in the Utilities folder in the Applications folder.
'Empty Trash...' will remove tags and icons of files, effectively making them 'invisible', but won't remove – as in destroy – the files themselves. The trashed files themselves, often really hundreds of snippets of those files in just as many different physical locations on the HD, get overwritten by other files on an as needed basis in the run of the HD's day-to-day disk space management.
'Secure Empty Trash' overwrites trashed files 7 times with random zeroes and ones, which is the current DoD spec, afaik. So 'Secure Empty Trash' takes time, isn't virtually instant, like the standard 'Empty Trash'. Sure, data can theoretically still be retrieved: a Cray supercomputer can do it, IF it gets 6 months processing time, to recover possible 'secret' data from this guy's Mac's harddisk!
Imagine the cost...
'Erase Free Space' in the Disk Utility is for those of us who don't even trust the DoD spec: it overwrites the disk's free space, i.e. trashed files, 35 times!
That is very time and processor intensive! So better let your Mac do that overnight.
But only Darth Vader can get those files back . . .
Comments
To completely delete the files in the Trash, got to the Finder menu and select "Secure Empty Trash"
Will that function work only on the most recently deleted items in Trash, or even items deleted earlier in Trash?
To erase the free space on the disk, use Disk Utility's "Erase Free Space" button under the "Erase" tab. This zeroes out all of the free space, which is where previously deleted Trash items would be.
Disk Utility is in the Utilities folder in the Applications folder.
'Empty Trash...' will remove tags and icons of files, effectively making them 'invisible', but won't remove – as in destroy – the files themselves. The trashed files themselves, often really hundreds of snippets of those files in just as many different physical locations on the HD, get overwritten by other files on an as needed basis in the run of the HD's day-to-day disk space management.
'Secure Empty Trash' overwrites trashed files 7 times with random zeroes and ones, which is the current DoD spec, afaik. So 'Secure Empty Trash' takes time, isn't virtually instant, like the standard 'Empty Trash'. Sure, data can theoretically still be retrieved: a Cray supercomputer can do it, IF it gets 6 months processing time, to recover possible 'secret' data from this guy's Mac's harddisk!
Imagine the cost...
'Erase Free Space' in the Disk Utility is for those of us who don't even trust the DoD spec: it overwrites the disk's free space, i.e. trashed files, 35 times!
That is very time and processor intensive! So better let your Mac do that overnight.
But only Darth Vader can get those files back . . .
Have fun!