Limit shares available via RWW

Open Notepad as administrator.

Open C:\Program Files\Windows Small Business Server\Bin\WebApp\RemoteAccess\web.config

Find and comment out this line:
<wssg.storageProvider type="Microsoft.WindowsServerSolutions.Web.Storage.SBSStorageProvider, Wssg.Web.StorageProvider" />

Add on next line:
<wssg.storageProvider type="Microsoft.WindowsServerSolutions.Web.Storage.FileSystemBasedStorageInformationProvider, Wssg.Web.Internal" shares="\\Server1\Share1;\\Server2\Share2;" />

Source: JacksonTechnical