How can I deny access to public folder files on the Apache server?

Try putting a .htaccess in the root of the project this way:

Options -Indexes
IndexIgnore *
<FilesMatch "\.(htaccess|htpasswd|ini|jpg|log|bak|txt)$">
 Order Allow,Deny
 Deny from all
 Allow from 192.168.0.9
</FilesMatch>

But the tmb files are blocked in the system and the only thing I want is that they can not be accessed by means of the navigation bar.