Files with grt extension may be also sometimes found as files that were encrypted and renamed by a variant of HiddenTear ransomware called Karmen.
There is one other file type using
the GRT file extension!
.grt - MegaHAL greeting file
GRT file extension - Karmen HiddenTear (variant) ransomware affected file
What is grt file? How to open grt files?
File type specification:
File extension grt seems to be also used by a variant of HiddenTear ransomware described as Karmen.
Much like other similar ransomware, it encrypts and renames affected files and demands payment in bitcoins for the decryption key.