.UNK File Extension
File TypeUnknown File
What is a UNK file?
Unknown file that does not have a file association; may contain file contents from an original file that was unrecognized by any program; created typically as a default extension for a corrupted or unknown file that is found in email attachments or downloads from the Web.
NOTE: Do not attempt to open UNK files unless you are certain of their content since they may contain a virus.