User-agent: *
Disallow: /?s=*
2. Block by htaccess
RewriteEngine on
RewriteCond %{QUERY_STRING} (/?s=) [NC]
RewriteCond %{HTTP_REFERER} !^https://(www\.)?bbb.com/.*$ [NC]
RewriteRule .* - [F,L]
Remember change bbb.com
by your url (google.com
for example)