I block AWS. So many crawlers up to so much nonsense! I don't block by IP, but by hostname.

  $block='.amazonaws.com';
  $ua = @$_SERVER['HTTP_USER_AGENT'];
  
  if (stripos($rh,$block)!==false &&
  	stripos($ua,'Silk')===false &&
  	stripos($ua,'Safari')===false){
  
    	$block_visitor=true;
  	$message="Blocked Host:Amazon Web Services";
  }