Macworld Forums

Macworld Forums: How to securely delete files - Macworld Forums

Jump to content

  • (5 Pages)
  • +
  • 1
  • 2
  • 3
  • Last »
  • You cannot start a new topic
  • You cannot reply to this topic

How to securely delete files

#1 User is offline   Macworld 

  • Story Poster
  • Group: MW Bot
  • Posts: 34,402
  • Joined: 30-November 07

Posted 28 March 2012 - 08:46 AM

Post your comments for How to securely delete files here
0

#2 User is offline   linkman 

  • Member
  • PipPip
  • Group: Members
  • Posts: 69
  • Joined: 18-February 09

  Posted 28 March 2012 - 09:11 AM

How secure is the Secure Empty Trash function compared to a single pass Zero Out Deleted Files?
0

#3 User is offline   FlopTech 

  • Member
  • PipPip
  • Group: Members
  • Posts: 108
  • Joined: 31-January 12

  Posted 28 March 2012 - 09:15 AM

Of course, if you're really truly paranoid, you won't sell your Mac until you've physically replaced its hard drive with a brand new one and installed OS X on it. And you'll keep your original hard drive, preferably in a fire-proof safe. Or you'll destroy that hard drive by disassembling it and physically destroying each platter after you've copied its contents to a new Mac (and verified the data.)
0

#4 User is offline   Chris Breen 

  • Advanced Member
  • Group: Moderators
  • Posts: 6,316
  • Joined: 11-December 00

Posted 28 March 2012 - 09:17 AM

View Postlinkman, on 28 March 2012 - 09:11 AM, said:

How secure is the Secure Empty Trash function compared to a single pass Zero Out Deleted Files?


My understanding is that Secure Empty Trash does the same thing as Zero Out -- so, one pass on the area.

#5 User is offline   MEPace 

  • Member
  • PipPip
  • Group: Members
  • Posts: 51
  • Joined: 20-May 10

Posted 28 March 2012 - 09:24 AM

View PostFlopTech, on 28 March 2012 - 09:15 AM, said:

Of course, if you're really truly paranoid, you won't sell your Mac until you've physically replaced its hard drive with a brand new one and installed OS X on it. And you'll keep your original hard drive, preferably in a fire-proof safe. Or you'll destroy that hard drive by disassembling it and physically destroying each platter after you've copied its contents to a new Mac (and verified the data.)

Best to take off and nuke the entire drive from orbit, it's the only way to be sure.
1

#6 User is offline   immovableobject 

  • Member
  • PipPip
  • Group: New Members
  • Posts: 17
  • Joined: 03-March 12

  Posted 28 March 2012 - 09:54 AM

This discussion assume you have a hard disk, not a solid state (flash RAM-based) drive. I don't know the particulars, but due to wear leveling algorithms, I suspect that securely deleting data against any type of forensic recovery is more difficult with SSDs.
0

#7 User is offline   MattS 

  • Newbie
  • Pip
  • Group: New Members
  • Posts: 5
  • Joined: 28-March 12

Posted 28 March 2012 - 09:58 AM

View PostMEPace, on 28 March 2012 - 09:24 AM, said:

View PostFlopTech, on 28 March 2012 - 09:15 AM, said:

Of course, if you're really truly paranoid, you won't sell your Mac until you've physically replaced its hard drive with a brand new one and installed OS X on it. And you'll keep your original hard drive, preferably in a fire-proof safe. Or you'll destroy that hard drive by disassembling it and physically destroying each platter after you've copied its contents to a new Mac (and verified the data.)

Best to take off and nuke the entire drive from orbit, it's the only way to be sure.


Aliens, man. Aliens.
0

#8 User is offline   bastion 

  • Power User
  • PipPipPipPip
  • Group: Members
  • Posts: 9,272
  • Joined: 14-October 04

Posted 28 March 2012 - 09:58 AM

View PostChris Breen, on 28 March 2012 - 09:17 AM, said:

View Postlinkman, on 28 March 2012 - 09:11 AM, said:

How secure is the Secure Empty Trash function compared to a single pass Zero Out Deleted Files?


My understanding is that Secure Empty Trash does the same thing as Zero Out -- so, one pass on the area.


I can't say for sure about Lion but when the Secure Empty Trash command was introduced it was using the 7-pass mode.
0

#9 User is offline   Success 

  • Member
  • PipPip
  • Group: Members
  • Posts: 158
  • Joined: 20-January 09

  Posted 28 March 2012 - 09:59 AM

I thought the only sure method was to burn the disk. Is this not so?
0

#10 User is offline   bastion 

  • Power User
  • PipPipPipPip
  • Group: Members
  • Posts: 9,272
  • Joined: 14-October 04

Posted 28 March 2012 - 10:04 AM

View Postimmovableobject, on 28 March 2012 - 09:54 AM, said:

This discussion assume you have a hard disk, not a solid state (flash RAM-based) drive. I don't know the particulars, but due to wear leveling algorithms, I suspect that securely deleting data against any type of forensic recovery is more difficult with SSDs.


With the proper software you can issue a command to an SSD that will wipe the entire thing. There's no reliable way to just do single files, though. Worse, I'm not aware of any Mac-native software that will issue the wipe command. You have to temporarily boot a different OS.
0

#11 User is offline   bastion 

  • Power User
  • PipPipPipPip
  • Group: Members
  • Posts: 9,272
  • Joined: 14-October 04

Posted 28 March 2012 - 10:08 AM

View PostSuccess, on 28 March 2012 - 09:59 AM, said:

I thought the only sure method was to burn the disk. Is this not so?


Technically, yes. Practically there are very few people who need anything more than the single-pass. The 35-pass mode is intentionally overkill; when it was originally described the intention was that you would pick a subset of it.

Just to be clear: The multi-pass modes aren't just writing zeros or purely random data over and over. They're writing a sequence of bit patterns, some of which are random and some specified. The idea is to introduce sufficient confusion into the magnetic field that there's no reliable way to determine the original bit value.
1

#12 User is offline   len5 

  • Member
  • PipPip
  • Group: Members
  • Posts: 181
  • Joined: 17-October 08

  Posted 28 March 2012 - 10:23 AM

I have an MBP 4,1 that I've installed an intel 320 SSD in. Most of what i've read about using Disk Utility's Secure Erase on an SSD hasn't been good. Especially with regards to drive performance. So instead I use Lion's FileVault 2 which encrypts the entire drive. That makes both your data and the free space on the drive totally secure. That is if you've used a strong password.
0

#13 User is offline   AdamS 

  • Newbie
  • Pip
  • Group: Members
  • Posts: 14
  • Joined: 25-January 07

Posted 28 March 2012 - 10:30 AM

View PostChris Breen, on 28 March 2012 - 09:17 AM, said:

View Postlinkman, on 28 March 2012 - 09:11 AM, said:

How secure is the Secure Empty Trash function compared to a single pass Zero Out Deleted Files?


My understanding is that Secure Empty Trash does the same thing as Zero Out -- so, one pass on the area.


I think it uses 35 passes, which is what the Unix command srm uses by default.
0

#14 User is offline   bastion 

  • Power User
  • PipPipPipPip
  • Group: Members
  • Posts: 9,272
  • Joined: 14-October 04

Posted 28 March 2012 - 10:38 AM

View PostAdamS, on 28 March 2012 - 10:30 AM, said:

View PostChris Breen, on 28 March 2012 - 09:17 AM, said:

View Postlinkman, on 28 March 2012 - 09:11 AM, said:

How secure is the Secure Empty Trash function compared to a single pass Zero Out Deleted Files?


My understanding is that Secure Empty Trash does the same thing as Zero Out -- so, one pass on the area.


I think it uses 35 passes, which is what the Unix command srm uses by default.


It does not use the 35-pass mode. The user base at large would be screaming their heads off if it did because almost no one has the patience for that on any substantial amount of data.

Apple also doesn't use srm for this functionality. They did originally but in, IIRC, Snow Leopard they started using their own tool that handles several different potentially high-risk disk activities. (Presumably so Finder didn't need elevated privileges.)

(Later) Actually it was Leopard, and the tool they switched to is called Locum.

This post has been edited by bastion: 28 March 2012 - 10:42 AM

0

Share this topic:


  • (5 Pages)
  • +
  • 1
  • 2
  • 3
  • Last »
  • You cannot start a new topic
  • You cannot reply to this topic

1 User(s) are reading this topic
0 members, 1 guests, 0 anonymous users