Merry X-Mas is a ransomware that was first spotted in the wild on January 3, 2017. Upon successful infection, the ransomware encrypts victims’ files and presents a “Merry Christmas” ransom note with a holiday-themed design and a demand for payment to regain access to the files.

http://blog.checkpoint.com/2017/03/14/merry-x-mas-ransomware-decryption-tool/