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When setting up a share on entire drive in Windwos 2k3 I get a message "You have chosen to share an entire drive For security reasons, this is not recommended". I did a quick googling but could not find these mysterious security reasons. Does anyone know what are they?

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up vote 6 down vote accepted

If you're sharing your system disk then all sensitive system information will be shared. If you provide write access, things could get even worse! Remote users will be able to get to the registry and at least check it's contents for possible passwords, keys and other "secret" information. If you give them write access, your whole system might be formatted by an unhappy visitor.

If you share a secondary disk, the risks are much smaller. Still, every visitor will have access to the full content of this disk so they will all be able to collect the sensitive information.

What many people don't realize is that Windows might already has a default share for most disks, which you can access by using something like:


Is this a security risk? Yes, and no. Depends on how secure the data on the disk needs to be. The main risk with shared drives is directly linked to every user who will access them. The more people who will access it, the bigger your risks will be. And remember: if your computer is connected straight to the Internet, almost everyone with an Internet connection might be able to access it. (Although this depends on your firewall settings.)

There are risks and the warning is meant to discourage people from just opening new shares just out of convenience, without thinking about possible consequences. Basically, you're opening another gate to your computer. It's like keeping the door of your car unlocked. In your garage, it would still be safe. Parked on the streets, there is a minor risk, although most people are just honest enough not to steal from you.

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This does not sound logical ( is Microsoft logical?). I should get a same warning trying to share %swindir% folder but I don't. – Sergei Aug 24 '09 at 11:41
Windows tries to catch the most common mistakes, not all of them. If you add the win dir, how about program files? Your own files? The list would be a) endless and b) highly disputed. But sharing the whole drive is a pretty safe bet: "User doesn't know what he's doind." – Aaron Digulla Aug 24 '09 at 14:18
And also, everything in %windir% is protected by filesystem ACLs. – grawity Aug 24 '09 at 16:27

It's just a "seriously dude, have you thought about this because it you haven't you could be doing kind of a bad thing but if you have thought about it then go ahead, be my guest" type message. Take it's advice, think it over first.

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..but I can share %windir% without taking advise I guess :) – Sergei Aug 24 '09 at 11:43

The risk of sharing an entire drive is greater than sharing part of it for the simple fact you are exposing the entire drive. It comes down to the golden rule of reducing the surface area available for attack.

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Yea, it really just is there to make you think about what you're doing first.

Whether there's security implications are not depends on what's on the drive. I'm not aware of any specific problem with a share being an entire drive.

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Thank you.Seems like Microsoft belives they know better what is secure and what not on my disk. – Sergei Aug 24 '09 at 11:38

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