I read on news websites of a new virus called crypto locket but the Symantec blogs or its website has no mention of it. Is it a real threat or a bogus alarm?
You can find a Symantec blog post about it here (it's very real - to safeguard your data, make sure you have backed up to an external drive that you disconnect from your network / PC when not in use, or to online storage):
Here is the detection names by AV's (though some are just a generic detection). for just 1 dropper.
There are currently 3 users online.