Stop WordPress Comment Spam

gistfile1.txt

// check to see if the hidden input exists in submission
function preprocess_new_comment($commentdata) {
	if(!isset($_POST['is_legit'])) {
		die();
	}
	return $commentdata;
}
add_action('preprocess_comment', 'preprocess_new_comment');

// add hidden field to form
function add_field_to_comment_form() {
	?>
	<script>
	jQuery( document ).ready( function($) {
		$('#commentform').prepend('<input type="hidden" name="is_legit" value="1" />');
	});
	</script>
	<?
}
add_action( 'wp_footer', 'add_field_to_comment_form' );