If you receive a mail masquerading as a company’s invoice and containing a Microsoft Word file, think twice before clicking on it.
Doing so could cripple your system and could lead to a catastrophic destruction.

Hackers are believed to be carrying out social engineering hoaxes by adopting eye-catching subjects in the spam emails and compromised websites to lure the victims into installing a deadly ransomware, dubbed “Locky,” into their systems.

So if you find .locky extension files on your network shares,
Congratulations! You are infected and left with just two solutions: Rebuild your PC from scratch or Pay the ransom.
Locky ransomware is spreading at the rate of 4000 new infections per hour, which means approximately 100,000 new infections per day.

Source & Credit : http://thehackernews.com/2016/02/locky-ransomware-decrypt.html