Ransomware encrypts an organisation's data and demands a ransom to restore it. Government bodies, hospitals and revenue agencies are prime targets, because every hour of downtime has a human and political cost.
The 3-2-1 backup rule
Keep 3 copies of your data, on 2 different media, with 1 offline or off-site. A backup reachable from the network will be encrypted along with everything else.
A tested recovery plan
A disaster recovery plan that has never been exercised is a hypothesis. We recommend at least one drill a year, with a recovery time objective (RTO) and an acceptable data loss (RPO) set by management.
The question is no longer whether you will be attacked, but when, and how fast you will restart.