Custom Pattern for Antispam Bee: Everything is spam with 6 numbers only *and* yandex.ru or yandex.com in the email field:

custom-pattern.php

<?php
/**
 * Plugin Name: Custom Patterns for Antispam Bee
 * Description: Add custom patterns for Antispam Bee.
 * Plugin URI:  https://torstenlandsiedel.de
 * Version:     1.0
 * Author:      Torsten Landsiedel
 * Author URI:  https://torstenlandsiedel.de
 * Licence:     GPL 2
 * License URI: http://opensource.org/licenses/GPL-2.0
 * Gist Plugin URI: https://gist.github.com/Zodiac1978/19c5b045515ee62b09702361369ea38f/
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly.
}

/**
 * Antispam Bee filter for custom RegExp patterns
 */
add_filter( 'antispam_bee_patterns', 'antispam_bee_add_custom_patterns' );

/**
 * Add more RegExp patterns
 *
 * @param   Array $patterns All RegExp patterns from ASB.
 */
function antispam_bee_add_custom_patterns( $patterns ) {
	
  $patterns[] = array(
		'body'   => '^[1-9]{6}$',
		'email' => '@yandex\.(ru|com)',
	);

	return $patterns;
}