[unisog] Windows Encrypted File System (EFS)

Clyde Hoadley hoadleyc at mscd.edu
Thu Feb 9 21:19:13 GMT 2006


I acknowledge that there are a lot of things I just don't know very
much about.  Windows Encrypted File System (EFS) is a good example
of something I know very little about.

Do I understand the following correctly?

If a Windows user copies a file from an EFS folder onto a USB drive,
the copy on the USB drive is not encrypted.  Is that true?

If a Windows user attaches a file from an EFS folder to an Email
message, the attachment is not encrypted?  The same is true
if they were to FTP the file.  Is that true?

There is malware (virus, worms, Trojans) that run in the context
of the logged on user.  Some of these are known to transmit
random files off of the victims computer to places unknown.
Wouldn't such malware, running in the context of the logged on user,
have access to EFS files?  If it should randomly select an EFS file
for transmittal (via Email, IM, ftp, etc...) the file be transmitted
unencrypted?  Is that true?

Laptop is joined to the domain, and while at work, the user
logges into the domain and works on some EFS files (on the laptop),
then they log off and take the laptop home.  The user will not be
able to access their EFS files on the laptop using a local account.
Is that true?

EFS is intended to protect files stored on the hard drive.  It does
not protect files that are being shipped off-site.  Is that true?

My gut feeling is that EFS, while good, it isn't a complete
encryption solution.  Some users may need additional encryption
solutions.  I also get the feeling that EFS could create more
problems that it solves.  What is your opinion?

-- 
Clyde Hoadley, CISSP, GSEC
Security & Disaster Recovery Coordinator
Department of Information Technology
Metropolitan State College of Denver
http://www.mscd.edu/~infotech/security/
<hoadleyc at mscd.edu>
(303) 556-5074 (office)
(720) 232-4737 (personal cell)



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