These are embedded operating systems, much like the BIOS in your 
router, and are not vulnerable to anything other then a BIOS attack 
which would have to be specific to whatever custom embedded OS is 
being used. Such a custom written virus would be extremely unlikely.

There are many routers now, that allow you to plug in a USB drive and 
be used as a network device, exactly like you would use a network 
printer. There are also devices that you can buy that you plug into 
your router, and then use as a USB drive network hub that do 
essentially the same thing. Performance is ho hum but such devices 
are used for media streaming, backup, data web access, and, as such, 
don't require much in the way of performance.

These devices are an excellent alternative to a server when all you 
desire is to share data on a small home network. All you have to do 
is plug them in and use them, and they have the added advantage of 
very small power requirements.

Mark Rode

At 07:50 AM 10/8/2010, you wrote:
>How does this work?  Is there some kind of an operating system on 
>the NAS?  Is it connected to one computer and back-ups are made 
>through the one computer?
>What do you do to prevent malware?
>  But, to leave a drive on 24/7  that is somehow connected to all 
> the computers at the same time suggests that there is some kind of 
> operating system that might be vulnerable.

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