"On further inspection, though, we have discovered that CryptoFortress includes the new and nasty feature of being able to encrypt files over network shares even if they are not mapped to a drive letter."Source : BC
.....
"this ransomware will also attempt to enumerate all open network SMB shares and encrypt any that are found."
http://www.bleepingcomputer.com/forums/t/569157/cryptofortress-a-torrentlocker-clone-that-also-encrypts-unmapped-network-shares/
Bad news anyway.
How secure is Norton's backup?