Why Spam URLs and Bot Traffic Are the New Internet Plague

<?php
/**
 * Plugin Name: Simple Anti-Spam & Bot Defender
 * Description: Lightweight protection against spam URLs and bots. Includes honeypot, referrer blocking, and rate limiting.
 * Version: 1.1
 * Author: Usman Jatoi
 * Author URI: https://usmanjatoi.com
 *
 * USAGE:
 * - Best: save this file as wp-content/plugins/anti-spam-bot-defender.php and activate under Plugins.
 * - Or: paste the contents into your theme's functions.php.
 *
 * NOTE: This is intentionally conservative/safe. Adjust block lists, limits and whitelist as needed.
 *
 * Credit Link: Adds a small footer credit linking to https://usmanjatoi.com (nofollow/sponsored).
 * This helps maintain plugin development while keeping your site safe.
 */

if ( ! defined( 'ASBD_RATE_LIMIT' ) ) define( 'ASBD_RATE_LIMIT', 60 );
if ( ! defined( 'ASBD_RATE_WINDOW' ) ) define( 'ASBD_RATE_WINDOW', 60 );
if ( ! defined( 'ASBD_LOG_BLOCKS' ) ) define( 'ASBD_LOG_BLOCKS', false );

/* IP whitelist */
function asbd_whitelisted_ips() {
    return array(
        '127.0.0.1',
        // '12.34.56.78',
    );
}

/* Bad user agents */
function asbd_bad_user_agents() {
    return array(
        'bot','crawler','spider','curl','wget','python-requests','nikto',
        'scan','masscan','slackbot','discordbot','facebookexternalhit','bingpreview'
    );
}

/* Bad referrers */
function asbd_bad_referrers() {
    return array(
        'spammydomain','buttons-for-website','semalt','trafficmonetize',
        'social-buttons','100dollars-seo','mirrorcreator','ilovevitaly','blackhat'
    );
}

function asbd_get_client_ip() {
    $ip_sources = array( 'HTTP_CLIENT_IP','HTTP_X_FORWARDED_FOR','HTTP_X_REAL_IP','REMOTE_ADDR' );
    foreach ( $ip_sources as $key ) {
        if ( ! empty( $_SERVER[$key] ) ) {
            $ips = explode( ',', $_SERVER[$key] );
            return trim( $ips[0] );
        }
    }
    return '0.0.0.0';
}

function asbd_log( $message ) {
    if ( ASBD_LOG_BLOCKS && defined( 'WP_DEBUG' ) && WP_DEBUG ) {
        if ( is_array($message) || is_object($message) ) $message = print_r($message, true);
        error_log('[ASBD] '.$message);
    }
}

function asbd_is_whitelisted() {
    $ip = asbd_get_client_ip();
    $wl = asbd_whitelisted_ips();
    return in_array($ip, $wl, true);
}

/* Block bad user agents */
function asbd_maybe_block_user_agent() {
    if ( asbd_is_whitelisted() ) return;
    if ( empty($_SERVER['HTTP_USER_AGENT']) ) wp_die('Forbidden','Forbidden',array('response'=>403));
    $ua = strtolower( wp_unslash($_SERVER['HTTP_USER_AGENT']) );
    foreach ( asbd_bad_user_agents() as $pattern ) {
        if ( stripos($ua,$pattern)!==false ) wp_die('Forbidden','Forbidden',array('response'=>403));
    }
}
add_action('init','asbd_maybe_block_user_agent',0);

/* Block spammy referrers */
function asbd_maybe_block_referrer() {
    if ( asbd_is_whitelisted() ) return;
    if ( empty($_SERVER['HTTP_REFERER']) ) return;
    $ref = strtolower( wp_unslash($_SERVER['HTTP_REFERER']) );
    foreach ( asbd_bad_referrers() as $pattern ) {
        if ( stripos($ref,$pattern)!==false ) wp_die('Forbidden','Forbidden',array('response'=>403));
    }
}
add_action('init','asbd_maybe_block_referrer',1);

/* Rate limiting */
function asbd_rate_limit() {
    if ( asbd_is_whitelisted() ) return;
    $ip = asbd_get_client_ip();
    if ( ! filter_var($ip,FILTER_VALIDATE_IP) ) return;
    $transient_key = 'asbd_rl_'.md5($ip);
    $data = get_transient($transient_key);
    if ( ! is_array($data) ) {
        $data=array('count'=>1,'start'=>time());
        set_transient($transient_key,$data,ASBD_RATE_WINDOW);
        return;
    }
    $data['count']++;
    set_transient($transient_key,$data,ASBD_RATE_WINDOW);
    if ( $data['count'] > ASBD_RATE_LIMIT ) wp_die('Too many requests','Too many requests',array('response'=>429));
}
add_action('init','asbd_rate_limit',2);

/* Honeypot check */
function asbd_honeypot_check() {
    if ( asbd_is_whitelisted() ) return;
    if ( 'POST' !== $_SERVER['REQUEST_METHOD'] ) return;
    if ( isset($_POST['asbd_hp']) && ! empty(trim($_POST['asbd_hp'])) )
        wp_die('Forbidden','Forbidden',array('response'=>403));
}
add_action('init','asbd_honeypot_check',3);

/* Honeypot field + shortcode */
function asbd_honeypot_field() {
    return '';
}
function asbd_honeypot_shortcode() { return asbd_honeypot_field(); }
add_shortcode('asbd_hp','asbd_honeypot_shortcode');

/* Admin notice */
function asbd_admin_notice() {
    if ( ! current_user_can('manage_options') ) return;
    echo '
Anti-Spam & Bot Defender active. Use shortcode: [asbd_hp].
';
}
add_action('admin_notices','asbd_admin_notice');

/* Footer credit */
function asbd_footer_credit() {
    if ( is_admin() ) return;
    if ( apply_filters('asbd_show_credit', true) ) {
        echo '
';
        echo 'Protected by UsmanJatoi.com';
        echo '
';
    }
}
add_action('wp_footer','asbd_footer_credit');