This is file spammer.php file in forum directory

<?php
  2
  3 if(strtolower($_REQUEST['app']) == 'core' && strtolower($_REQUEST['module']) == 'global' && strtolower($_REQUEST['section']) == 'register') {
  4
  5 define("MAX_POST_COUNT", 3);
  6 define("POST_DELAY", 150);
  7 define("BAN_TIME", 7200);
  8
  9 include('conf_global.php');
 10
 11 $mysqli = new mysqli($INFO['sql_host'], $INFO['sql_user'], $INFO['sql_pass'], $INFO['sql_database']) or die("Sql Error");
 12
 13 if(mysqli_connect_errno()) {
 14     printf("Connect failed: %sn", mysqli_connect_error());
 15         exit();
 16 }
 17
 18 $ip = ip2long($_SERVER['REMOTE_ADDR']);
 19
 20 $query = "SELECT LAST_POST_TIME, POST_COUNT, BLOCKED FROM SPAMMER_IPS WHERE IP = $ip;";
 21 $result = $mysqli->query($query);
 22
 23 if($mysqli->affected_rows > 0) {
 24     $row = $result->fetch_assoc();
 25
 26     $current_time = time();
 27     $last_post_time = strtotime($row['LAST_POST_TIME']);
 28
 29     $time_diff = $current_time - $last_post_time;
 30
 31     if($row['POST_COUNT'] >= MAX_POST_COUNT) {
 32         if($time_diff < BAN_TIME) {
 33             $query = "UPDATE SPAMMER_IPS SET LAST_POST_TIME = NOW(), POST_COUNT = POST_COUNT + 1 WHERE IP = $ip;";
 34             $mysqli->query($query);
 35
 36             header('HTTP/1.0 404 Not Found');
 37             exit;
 38         }
 39         else {
 40             $query = "DELETE FROM SPAMMER_IPS WHERE IP = $ip;";
 41             $mysqli->query($query);
 42         }
 43     }
 44     else {
 45         if($time_diff < POST_DELAY) {
 46             $query = "UPDATE SPAMMER_IPS SET LAST_POST_TIME = NOW(), POST_COUNT = POST_COUNT + 1 WHERE IP = $ip;";
 47         }
 48         else {
 49             $query = "DELETE FROM SPAMMER_IPS WHERE IP = $ip;";
 50         }
 51
 52         $mysqli->query($query);
 53     }
 54 }
 55 else {
 56     $query = "INSERT INTO SPAMMER_IPS (IP, POST_COUNT) VALUES ($ip, 1);";
 57     $mysqli->query($query);
 58 }
 59
 60 mysqli_close($mysqi);
 61
 62 }
 63
 64 ?>

This is SPAMMER_IPS table

DROP TABLE IF EXISTS `SPAMMER_IPS`;
CREATE TABLE IF NOT EXISTS `SPAMMER_IPS` (
  `IP` int(4) unsigned NOT NULL,
  `LAST_POST_TIME` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `POST_COUNT` int(2) unsigned NOT NULL DEFAULT '0'
  PRIMARY KEY (`IP`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;

And the last one you need to add this line

include('spammer.php');

in forum/index.php

  1 <?php
  2 /**
  3  * <pre>
  4  * Invision Power Services
  5  * IP.Board v3.4.6
  6  * Main public executable wrapper.
  7  * Set-up and load module to run
  8  * Last Updated: $Date: 2013-02-26 08:08:06 -0500 (Tue, 26 Feb 2013) $
  9  * </pre>
 10  *
 11  * @author      $Author: mark $
 12  * @copyright   © 2001 - 2009 Invision Power Services, Inc.
 13  * @license     http://www.invisionpower.com/company/standards.php#license
 14  * @package     IP.Board
 15  * @link        http://www.invisionpower.com
 16  * @version     $Rev: 12025 $
 17  *
 18  */
 19
 20 include('spammer.php');
 21
 22 define( 'IPB_THIS_SCRIPT', 'public' );
 23 require_once( './initdata.php' );/*noLibHook*/
 24
 25 require_once( IPS_ROOT_PATH . 'sources/base/ipsRegistry.php' );/*noLibHook*/
 26 require_once( IPS_ROOT_PATH . 'sources/base/ipsController.php' );/*noLibHook*/
 27 ipsController::run();
 28
 29 exit();

And after it spammers won't waste your traffic.

Yeah. And it's working only with MySQL. It's just quick fix for stop spammer registration tries.

That could probably be packaged up as a neat hook and submitted to the Marketplace. :)