I understand this isn’t exactly what you’re looking for but these hackers are most likely bots and redirecting them won’t matter at all. I suppose you could modify the below code if you reallllly wanted to but this will redirect anybody looking for an author back to your homepage.
RewriteCond %{REQUEST_URI} ^/$
RewriteCond %{QUERY_STRING} ^/?author=([0-9]*) [NC]
RewriteRule ^(.*)$ http://%{HTTP_HOST}/? [L,R=301,NC]