Lots of news out there this evening about a new Ransomware with auto-propogation ability. Please see our Talos blog post here: http://blog.talosintelligence.com/2017/05/wannacry.html
We have Snort coverage available in the form of rules:
42329-42332, 42340, 41978
This coverage is available in our Snort Subscriber Rule Set.
In order to subscribe now to Talos's newest rule detection functionality, you can subscribe for as low as $29 US dollars a year for personal users, be sure and see our business pricing as well at https://snort.org/products#rule_subscriptions.