If you are afraid of viruses, worms, or trojans....and want to protect your computer from users who use USB Drives now you can do that in windows 8.
USB storage devices are so common these days almost everyone owns USB storage device in shape of small flash drives, external hard disks, mobile phones, cameras, and lots of other portable devices.
So if you want to secure your computer from stealing data, viruses or any other risks then simply disable the USB ports for USB storage devices / disk drives.
To block the USB storage devices just follow the given steps below
press
Windows +
R from your keyboard then type
gpedit.msc then click
OK
when you got gpedit on Windows 8, expand:
Computer Configuration >
Administrative Templates >
System >
Device Installation >
Device Installation Restrictions >
Prevent installation of removable devices then tight click and choose
Edit 
From
Prevent installation of removable devices check
Enable then click
OK.
As with many Windows 8 Group Policies, check the logic, for instance, Prevent -- >
Enable.
Note: This means you cannot use the USB drive.
