Always include a blank index.html or an index.php file in every directory on your server. This forces the server to load the blank page rather than listing the underlying files.
Today, FLV files are mostly found in legacy web archives, older personal backups, or outdated media servers. The Security Implications of Exposed Server Directories index of flv sex
Cybercriminals sometimes inject malicious scripts or malware disguised as media files into unprotected directories, targeting unsuspecting downloaders. Always include a blank index