Re: looking for EFS weaknesses

From: Roger A. Grimes (rogergat_private)
Date: Fri Jun 27 2003 - 06:15:04 PDT

  • Next message: Tom Bowers: "Re: looking for EFS weaknesses"

    Randy, I believe the first problem you mention was fixed long ago in a
    service pack.  It does not store a plaintext copy on the hard drive anymore.
    
    The only problem I know about it is that on XP computers not belonging to a
    domain, the user's password is tied to the keys, so that if the user's
    password is changed or lost, the file will become unrecoverable to even the
    recovery agent.
    
    Roger
    
    ****************************************************************************
    ****
    *Roger A. Grimes, Computer Security Consultant
    *CPA, MCSE (NT/2000), CNE (3/4), A+
    *email: rogergat_private
    *cell: 757-615-3355
    *Author of Malicious Mobile Code:  Virus Protection for Windows by O'Reilly
    *http://www.oreilly.com/catalog/malmobcode
    ****************************************************************************
    *************
    
    ----- Original Message ----- 
    From: "Ryan Smith" <ryansmithat_private>
    To: <forensicsat_private>
    Sent: Thursday, June 26, 2003 11:53 AM
    Subject: looking for EFS weaknesses
    
    
    >
    >
    > After some research, I am considering rolling out an encryption solution
    > based on win2k EFS. I know of one weakness, that encrypting a file that
    > already exists will leave behind an insecurely deleted plaintext file.
    > This means anyone with any decent forensics tool could bypass the OS and
    > easily read it directly off the hard drive.
    >
    > It also transfers files insecurely across the network.  SSL should solve
    > for that.
    >
    > Does anyone know of any other major weaknesses in the EFS encryption,
    > certificate handling, encryption, etc?  For this group I'm particularly
    > looking for areas of the hard drive that may contain hidden plaintext
    > copies of normally encrypted documents.
    >
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