According to a year-end summary release by Trend Micro, incidents of ransomware increased by more than 7.5 times, and resulted in more than $1 billion in estimated losses. Ransomware locks systems using encryption or other methods to prevent access until a ransom is paid. Many businesses and government organizations elect to pay the ransom because they lack the proper backups to recover effectively from the attack. Always have regular backups, on a different system, and preferably isolated from the rest of the network to keep them from being affected by an attack.
For more information, refer to the following article: http://www.securityinfowatch.com/news/12311226/trend-micro-report-reveals-752-percent-increase-in-ransomware