Tool : Deadbolt Ransomware Decryptor
Official : Emsisoft
Usage : Free 

You got locked or encrypted your files with deadbolt ransomware ? Here is the tool from emsisoft you can try to decrypt your files. DeadBolt encrypts QNAP devices using AES-128, and appends the extension ".deadbolt".

(link downloads file from emsisoft site)

How to be safe :
1) use official antivirus
2) do not click unknown links
3) do not download crack softwares.