Roland, if you have even a USB pen Drive in a port with data on that will be targeted should a ransomware attack succeed, worse still is if the ransomware is set up to drop an additional payload for future use This can be a copy of it's own installer or some other payload like a bot net executable (this may even be encrypted amongst the files that the user who pays the ransom will set the secondary infection in motion. Also of course if an inserted USB Pen Drive is bootable (an installer maybe?), the malware payload will infect any system that it is used to install it's legitimate install on.

One way to lessen the potential impact of a malware attack is to either follow old IT practice and run as a standard user, only logging in as an admin account when you are forced to. Of course the UAC on Window 7 and later is a much more user friendly way of achieving the same security

Things have come on a long way since the 1980's when an intern of mine, (a modern term for a PFY (pimply faced Youth)) could beat the latest and greatest Pro antivirus of the day by opening the virus in a HEX editor and changing one Hex Digit in the ID string of the code, Just as a proof of concept or course