If you possess this specific file and are unsure of its origin, follow these steps to generate a local "deep report":
Use a tool like ExifTool to view the internal creation dates and authors, which may reveal its true purpose.
Compressed archives are frequently used by cybercriminals to hide malicious payloads from basic antivirus scans. A file named "Mil011.rar" (possibly shorthand for "Military" or a specific internal project code) that arrives from an unknown source should be treated as high-risk.