One of the computers in my office has been compromised by Cryptolocker. Once informed, my immediate response was to disconnect the computer from the network - though there was a period of a few hours in which I was not aware of the issue.
The infected computer was connected to a NAS drive, as well as multiple computers on the network. The NAS drive is publicly accessible, and some of the files therein were encrypted. The computers require separate access credentials, and do not appear to have been infected.
In this situation, are the other computers currently at risk of being infected? How exactly does Cryptolocker (or similar ransomware) propagate through networks? Could something have been done to better secure the NAS drive?