If you received this file from an unknown or unsolicited source outside of a known training platform, .
Note that there is also a popular macOS security tool called KnockKnock (distributed as a ZIP) that scans for persistent software; ensure you haven't confused the forensic file with this application. File: Who.Knocks.zip ...
If you are using this for a legitimate security exercise, you can inspect the contents without full extraction using these tools: If you received this file from an unknown