A new bootlocker called DiskWriter, or UselessDisk, has been discovered that overwrites the MBR of a victim’s computer and then displays a ransom screen on reboot instead of booting into Windows. This ransom note asks for $300 in bitcoins in order to gain access to Windows again. At this time, no payments have been made to this bitcoin address. The infection is being distributed under the DiskWriter.exe and Useless Disk.exe filenames. As more information becomes available, I feel that this infection was designed to be destructive and not actually be a ransomware.
Source: https://www.bleepingcomputer.com/news/security/the-diskwriter-or-uselessdisk-bootlocker-may-be-a-wiper/