Files with d4nk suffix can be most often found as files that have been encrypted and had their suffix renamed by PYL33T ransomware.
D4NK file extension - PyL33T ransomware affected file
What is d4nk file? How to open d4nk files?
File type specification:
File extension d4nk is mainly related to a ransomware that appeared in late February 2017 and was labeled as PyL33T. Much like other ransomware it encrypts users files and renames the suffix. Looks like the ransomware was written in Python.