: Upload the file to a service like VirusTotal to check it against dozens of different antivirus engines.

: If you must inspect it, do so within a virtual machine or a "sandbox" environment to prevent any potential scripts from affecting your primary operating system.

: It may be a custom archive created for a specific person or group (e.g., a "special" collection of 1,230 assets) that hasn't been indexed by search engines.

Knowing where you found the file name or what you expect to be inside (e.g., music, game assets, or code) would help in tracking down more specific information.