EFS, and why you shouldn't ever use it! - gHacks Tech News

EFS, and why you shouldn't ever use it!

Yesterday I wrote here about the BitLocker security file encryption system that was introduced with Windows Vista.  BitLocker is a full-disk encryption technology but I also alluded to problems with Microsoft's other encryption technology, EFS (Encrypted File System).  EFS has been with us for over a decade now and has slowly been improved by Microsoft.  I believe that it's an extremely good idea to encrypt your files and data, especially if you have a laptop, but certainly anything personal or financial on your main PCs if at all possible, or to at the very least make your PC secure with a strong password.

I would never recommend anybody ever use EFS however and here's why.  I'm extremely good with backups, I tell people all the time to make sure that they have adequate backups of their files and documents and I practice what I preach.  I use Windows Live Mesh to synchronise my documents, music and pictures between my main desktop and my laptop.  My main desktop then backs everything up to a second internal hard disk and also an external NAS (Network Attached Storage) drive.  I then have a secondary NAS drive which I keep off-site which I bring back every month or so to update the backup on that.  This is the way I recommend everybody does backups; though USB hard disks are just as effective as NAS drives and much cheaper.

I've lost files that I've backed up with EFS however, not only on my own computer but also on the NAS drives.  In fact I've only used EFS twice in the last ten years on my own computers and on both occasions I've lost files and documents.  I therefore cannot recommend you ever encrypt your files with this Windows feature.

The problems occur because EFS will encrypt any file that resides on an NTFS formatted disk, the default formatting option for XP, Vista and Windows 7 and also for the vast majority of USB hard disks and some NAS drives.  Unfortunately, because of incompatibilities with some differing versions of EFS files can end up scrambled and unrecoverable.  This wouldn't happen on a USB hard disk but I found it occur on my NAS box.  This means that if something goes wrong and you need to recover the backup from the drive, even the appropriate EFS key, that you would clearly have backed up and kept safe, won't unlock the files.  They will simply be lost and gone forever.

There's no way to know on what devices the EFS file scrambling will happen either.  With non-EFS supported devices, ie those that aren't formatted with NTFS, Windows will ask if you "want to copy the files without encryption" and will decrypt them on the fly.  Unlike BitLocker however, which just encrypts the hard disk, EFS encrypted files remain encrypted when copied off the machine to another NTFS formatted disk.

There are other problems with EFS too and these include metadata.  The EFS system, for reasons I've never been able to ascertain, is incompatible with the metadata you add to certain file types, pictures and photographs especially.  Not only will it strip out the metadata from these files, it will modify the files in such a way as to prevent you from adding the metadata back in afterwards, effectively making the file useless to you if this is how you like to organise your photos and pictures.

All of this comes from my own personal experience and it shows how even technical experts can be caught out by hardware and software incompatibilities and faults in, seemingly secure Windows features.  I would not recommend you ever use EFS.  If you have a laptop or desktop machine with a TPM chip and a copy of Windows Ultimate or Enterprise, use BitLocker.  If not the excellent TrueCrypt is a free utility that comes highly recommended by security experts worldwide.

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Comments

  1. GIddyUpGo said on September 11, 2011 at 3:54 pm
    Reply

    Mike, Is there a way to remove or disable EPS on W7 Pro.? There are others then me that use this computer.

  2. Robert Palmar said on September 11, 2011 at 6:32 pm
    Reply

    Wow.

    Although I have never chosen to use EFS,
    I certainly never will contemplate using it.

    You have made a strong case, Mike, for
    Microsoft to replace EFS in Windows 8.

  3. afrasim said on September 16, 2011 at 9:31 am
    Reply

    i have problem related to EFS, i have encrypted files without certificate for them, so i searched for solution, although there are plenty of softs which should solve this problem, but none of them helps. so if you have any idea, i’ll appreciate it.

  4. BobbySacks said on December 16, 2011 at 5:32 am
    Reply

    Can you describe the details of how to reproduce the error? Which versions of Windows have different versions of EFS, for example? Which NAS devices? How do you know it was EFS and not the NAS, such that the NAS is damaging other files in subtle ways that you haven’t detected yet? I’ve been using EFS for many years across all versions of Windows since 2001 and have yet to experience a corruption problem. Thanks.

  5. Chris said on July 19, 2012 at 1:07 pm
    Reply

    Hey everybody,
    I’ve used EFS with lots of laptops (170) with Windows XP and I never encountered file corruption or any other problems. I lost entire disks withh full disk encryption (FDE) due to MBR corruption that could not be recovered even with vendor dedicated software.
    I recommend using EFS to secure laptops and desktops instead FDE in enterprise environments that have a centrally managed certification authority with recovery agents.

  6. idont said on December 29, 2012 at 4:49 am
    Reply

    It is an old thread but still a present question…

    How have you identified EFS to be the source of the isssue? Reading your text, it looks like your are not using RAIDed disks on your main machine. Are you sure it was not a problem due to some “bad disk sector(s)”? Have you correctly exported the certificates?

    Thanks for your feedback.

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