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Recently we wrote about wp-vcd malware that created rogue WordPress admin users (100010010) and injected spam links.

Our readers noticed that the “nulled” premium theme sites promoted by the injected links (and some other similar sites) had this very wp-vcd malware pre-installed with every downloaded theme.

It’s pretty easy to notice when you check the files inside the downloaded .zip files. All original files have one date, but two files have a different, more recent date:


12914 Dec  4 09:25 functions.php
33045 Nov 30 09:33 class.theme-modules.php

And if you check those files, you’ll notice that functions.php has this line of code at the top

<?php if (file_exists(dirname(__FILE__) . '/class.theme-modules.php')) include_once(dirname(__FILE__) . '/class.theme-modules.php'); ?>

And class.theme-modules.php (the file that is included by the code added in the functions.php) is the file that installs the wp-vcd malware into the theme and creates the rest malicious files.

The beginning of the file looks like this

<?php
 
//install_code1
error_reporting(0);
ini_set('display_errors', 0);
DEFINE('MAX_LEVEL', 2); 
DEFINE('MAX_ITERATION', 50); 
DEFINE('P', $_SERVER['DOCUMENT_ROOT']);

$GLOBALS['WP_CD_CODE'] = 'PD9waHANCmVycm9y...long base64-encoded string here followed by installation code...
...

Providing “nulled” content with backdoors, spam and other types of malware is typical for sites that offer premium software “for free”. We warned against using nulled themes and plugins many times.

Cleaning sites with such malware may be not that easy as it downloads and installs more malware as soon as you begin using the contaminated theme or plugin. And the backdoor it creates allows the bad guys to do almost anything with your site. That’s why a thorough site analysis and cleanup is required. Let us know if you need our help.