If you have the file and are unsure of its contents, you can safely inspect it without playing it:
In some niche communities, "f" prefixes are used for specific archives: : Recordings of flight paths or maneuvers. f 473.39.mp4
This would help in narrow down its specific origin. If you have the file and are unsure
: Some privacy apps rename media to alphanumeric strings to obscure the content. 2. Check the File Metadata f 473.39.mp4
File names starting with a single letter followed by numbers (like "f 473...") are often generated by: