Tag Archives: Plugins WordPress

How to protect your WordPress site using PHP Firewall plugin

This article explains how you can protect your WordPress site from attacks using my PHP Firewall WordPress plugin version 1.0.8.

This plugin is a commercial plugin, with one time fee, that it’s absolute worth it. It is not available as free plugin lite in WordPress.org. Only in my Software store. It is also available as PHP Firewall Drupal module.

Once you install the plugin, you click in Enable protection and the Firewall will start to detect attempts to find exploits in your server automatically, and will block the offending IPs.

If you Enable count of blocked requests you’ll see than in few minutes, the Firewall has blocked hundreds of attempts.

In this example, I activated the protection, and after some time it has automatically detected and blocked 118 offending IP Addresses, and has blocked 195 malevolent requests.

In 36 hours the number of blocked requests will get to thousands:

Enabling the count of blocked requests makes a small update in the database to increment the counter, it’s a very lightweight operation, but it is worth it to get an idea of how many malevolent requests the software is blocking. You can enable it for an hour, see how many bad requests you get, and disable it if you want.

Once you activate the protection you will start to see IP Addresses that have been blocked because they attempted a known exploit, and the IPs have been added to the list of Automatic offenders.

This function is known as WAF or Web Application Firewall.

Once an IP is detected as offender, it will get a 403 Forbidden answer from the Server immediately, and the precious resources from the server will be saved (CPU, Memory, Internet bandwidth).

If you want, you can delete the IP from the list to allow it access again (for example, if a colleague was doing a test).

As you see, you will get many IP from attackers blocked in a short window of time.

The reality is that bots are trying exploits against random IP Addresses all the times, and some times your server will go very slow because of all those bots trying to hack into your server, and your visitors will experience slow loading pages or even the server may crash due to all these bots activity. Also, depending on your Cloud provider, you may be paying for Internet Outgoing traffic that is consumed by bots.

So this plugin is a must have, in my opinion as Engineer. That’s why I created it. Because many people was asking for help.

But there are other types of abuse. For example, malicious bots will try to get access to your blog by doing requests with random passwords to wp-login.php every second.

The Firewall cannot block this route by default because is the route that legit users use to login to WordPress. But we have functionalities in the plugin to deal with these attacks (without having to analyse the web server logs, which is a task that System Administrators and Site Reliability Engineers do).

Activate Enable log of non blocked requests for analysis

This will record every allowed request (not the blocked ones), so we can analyse them.

Just scroll down, to Latest requests

As you can see there are IP Addresses that did a POST to /wp-login.php

That means that attempted to login in your site. So, they tried a password to hack your WordPress site.

Those IP Addresses are attempting to login every second or every two seconds.

These kind of attacks are not only bad, as they can get access to your site, they can also degrade the health of your database.

You can investigate where these IP’s come from doing a Whois search, or asking Google: whois 50.87.179.84

So, it’s a hosting from Bluehost / HostGator, a Cloud Provider. Servers from Cloud providers are typically hacked to try to hack other servers.

You can block the IP directly in the PHP Firewall using the custom rules, or as you can see in the information provider, this Cloud Provider has a NetRange / CIDR of 50.87.0.0/16.

A block /16 comprises 65,536 IP Addresses, so you’ll probably get attacks from many different IP’s in from that block. Instead of blocking just the IP that attacked your site, my approach is to block all the IP’s from that block.

So we add to Manual IP deny rules the block:

The reasoning about blocking all the 65,536 IP Addresses from the Cloud provider is that your WordPress site is probably a site for humans. You want humans to read your blog posts, or if it’s an e-Commerce site, you want to sell to humans. You don’t want bots to use the resources of your server or to try to hack your server. So blocking Cloud Provider’s IP ranges, seems like a good strategy.

If you are one of the few WordPress sites with third party integrations that need to be reached from Cloud providers, you can avoid denying those blocks of IP Addresses that your partners use.

We investigate the other IP:

And it’s the same case, so we also block the CIDR Block in the PHP Firewall.

A /22 block comprises 1,024 IP Addresses. So, with two lines in our firewall we have blocked potential malicious requests from 66,560 IP Addresses.

Obviously we cannot analize all the requests we get, but Firewall PHP plugin provides a very useful tool that will display the IP Addresses that did more request to our server in the last 24 hours.

Just click on Show IPs with most requests (last 24h)

The top 50 IP Addresses that performed more requests are displayed:

In this case, the first IP Address belongs to my own IP Address. Which makes sense because WordPress opened in the browser keeps doing requests to the server.

As I activated the log at 17:26:16 and it’s 21:44:10 in around 4 hours and 15 minutes I got an IP Addresses that did 264 requests.

The IP 134.209.183.0 has performed 264 requests that went through.

If I check the logs of the server I see that it was attempting to hack the server (trying user/password on wp-login.php)

grep "134.209.183.0" *.log

As you can see, this IP was requesting 12 requests per second trying to hack into /wp-login.php

And if we do the whois of this IP Address, it belongs to Digital Ocean:

So we block the entire block 134.209.176.0/20 in the PHP Firewall.

Now the server will block any request from the 4,096 in that block range and will not spend time and resources that are intended for your human visitors.

Most of the attacks come from Cloud providers. Normally are servers that got hacked, and they used those servers to try to hack other servers.

PHP Firewall provides great help in protecting your sites, specially if you don’t have a dedicated team of System Engineers that check the logs regularly, and block the offending IP Addresses in the firewalls.

After 12 hours we see more IP Addresses that made thousands of requests:

According to google those IP Addresses belong to Oracle Cloud:

So, we block the CIDR Block: 137.23.0.0/16 (which will block the two offending IP Addresses, as they form part of that block)

In the latest requests we can see how are new IP Addresses scanning for authors in order to try to attempt logins:

As you can see this IP Address is doing 10 requests in the same second trying passwords (POST to /wp-login.php) in order to attempt to hack the WordPress site.

We do a whois search to see who is the owner of that IP Address:

Is from DigitalOcean, the Cloud Provider. We block all the Netblock 139.59.0.0/16

We see a new IP attacking the server, it is attempting two connections per second POST to /xmlrpc.php which tries to perform actions on the site. xmlrpc.php is a legit mechanism from WordPress, for example to register pingbacks, so it is not blocked by default. But hackers use xmlrpc.php to try thousands of passwords at once without passing by the login screen.

If you do not use older mobile apps or specific remote publishing tools that rely on it you sholud block xmlrpc.php

The whois shows that many attacks come from this provider:

The site AbuseIPDB flags that IP as an attacker with more than 5,000 reports: https://www.abuseipdb.com/check/78.142.18.40

We can block the 256 IP Addresses of the class C, so: 78.142.18.0/24

We will also block the requests to /xmlrpc.php using Custom URL patterns:

Later, we see that there are more IPs attacking trying to abuse wp-login.php so we will block them:

We check the IP that is doing so many attempts to hack requesting wp-login.php

And all the range has been flagged for automated malicious activity and brute-force attempts

So we block all the 256 IP (class C) 93.152.221.0/24.

Two days later I check the IPs doing more requests:

I looked at the logs what requests was doing the first IP:

All were attempts to hack the site through /wp-login.php

We check what kind of IP is this, and it’s from a Cloud provider:

So we block the range 141.98.11.0/24 in IP Firewall.

If you have SSH to the server you can block it in the firewall.

For Ubuntu, with ufw that is:

sudo ufw insert 1 deny from 141.98.11.0/24 to any

PHP Firewall WordPress plugin is a great help, as it blocks most of the attacks automatically, and offers you tools to detect the IPs that do more requests, so you can block them (or the entire range) easily, and to track the latest requests and export them.

Also, the price of the plugin is one time fee per site. Not a recurring payment.

There is also PHP Firewall Drupal module and a PrestaShop module.

If you want to acquire the Firewall rules that we have been collecting over the years, you can also buy the Firewall rules of Cloud providers from which we received attacks. These can be applied to any Firewall software, for instance Ubuntu ufw, or to my plugin/modules.

My PHP Script to see WordPress Posts and Views ordered by Views

This article shows the code for my PHP program posts_and_views.php that you can see at the bottom of in the Quick Selection bar.

Page rendered of all my Published Posts sorted by Views

So I wrote this small PHP Code to display the number of Post Views recorded in my WordPress Database, sorted by Views in descending order.

In other words, sorted from Most Viewed.

Please note: In order to track the post views I use the excellent plugin WP-PostViews by Lester ‘GaMerZ’ Chan

Here is the code for posts_and_views.php

As you can see I use wp-config.php file to get the Database Settings (username, password, database) but I don’t use the WordPress Engine, it is just a stand alone PHP. So I wrote my own function to get the slug based on the category name. I believe the slug for it is in the Database and I could have added this as a SubQuery with JOINs, which would be better, but I wanted to keep the Database workload lightweight and especially, I did not want to invest more time investigating how the get the slug.

As I tested my function I didn’t find any Category failing but I saw that I had the Category Storage repeated in two different structure tree in Categories, and I will only always link to just the first one (So I was not linkin to the slug storage-2). I fixed that Category that I found repeated but to be honest if this script was a commercial solution or an Open Source solution properly maintained rather than just a sample, I would update it to have Categories and Tags’ slugs coming from the Database.

I would probably make it work with a Cron that would generate a cached page, updated every hour or every ten minutes. I did this in other projects I worked or in my PHP Framework Catalonia Framerwork.

But honestly, the load of the page does not justify a major effort in optimizing here, in this case.

<!DOCTYPE html>
<html>
<head>
    <style>
        .first {

            background-color: blue;
            padding: 12px;
        }
        .second {
            background-color: rgba(254, 253, 252, 0.7);
            text-align: center;
            padding:20px 0;
            font-size: 20px;
        }

        .centered {
            text-align: center;
        }

        /* unvisited link */
        a:link {
            color: blue;
            text-decoration: none;
        }

        /* visited link */
        a:visited {
            color: blue;
            text-decoration: none;
        }

        /* mouse over link */
        a:hover {
            color: #00A8EF;
            text-decoration: underline;
        }

        /* selected link */
        a:active {
            color: blue;
        }
    </style>
<body>
<?php

include "wp-config.php";

$s_site_name = "Carles Mateo's blog";
$s_site_link = "https://blog.carlesmateo.com";

function get_category_slug($s_text) {
    $s_output_text = strtolower($s_text);
    $s_output_text = str_replace(" ", "-", $s_output_text);

    return $s_output_text;
}

?>
<h1><a href="<?php print $s_site_link; ?>"><?php print($s_site_name); ?></a></h1>
<?php


$s_sort = "views DESC, post_date, post_title DESC";

if (array_key_exists("sort", $_GET)) {
    if ($_GET["sort"] == "date") {
        $s_sort = "post_date, views, post_title";
    }
}

$s_servername = "localhost";
$s_database = DB_NAME;
$s_username = DB_USER;
$s_password = DB_PASSWORD;


// Create connection
$o_conn = new mysqli($s_servername, $s_username, $s_password, $s_database);

// Check connection
if ($o_conn->connect_error) {
    die("Connection failed: " . $o_conn->connect_error);
}

/*
mysql> DESCRIBE wp_posts;
+-----------------------+-----------------+------+-----+---------------------+----------------+
| Field                 | Type            | Null | Key | Default             | Extra          |
+-----------------------+-----------------+------+-----+---------------------+----------------+
| ID                    | bigint unsigned | NO   | PRI | NULL                | auto_increment |
| post_author           | bigint unsigned | NO   | MUL | 0                   |                |
| post_date             | datetime        | NO   |     | 0000-00-00 00:00:00 |                |
| post_date_gmt         | datetime        | NO   |     | 0000-00-00 00:00:00 |                |
| post_content          | longtext        | NO   |     | NULL                |                |
| post_title            | text            | NO   |     | NULL                |                |
| post_excerpt          | text            | NO   |     | NULL                |                |
| post_status           | varchar(20)     | NO   |     | publish             |                |
| comment_status        | varchar(20)     | NO   |     | open                |                |
| ping_status           | varchar(20)     | NO   |     | open                |                |
| post_password         | varchar(255)    | NO   |     |                     |                |
| post_name             | varchar(200)    | NO   | MUL |                     |                |
| to_ping               | text            | NO   |     | NULL                |                |
| pinged                | text            | NO   |     | NULL                |                |
| post_modified         | datetime        | NO   |     | 0000-00-00 00:00:00 |                |
| post_modified_gmt     | datetime        | NO   |     | 0000-00-00 00:00:00 |                |
| post_content_filtered | longtext        | NO   |     | NULL                |                |
| post_parent           | bigint unsigned | NO   | MUL | 0                   |                |
| guid                  | varchar(255)    | NO   |     |                     |                |
| menu_order            | int             | NO   |     | 0                   |                |
| post_type             | varchar(20)     | NO   | MUL | post                |                |
| post_mime_type        | varchar(100)    | NO   |     |                     |                |
| comment_count         | bigint          | NO   |     | 0                   |                |
+-----------------------+-----------------+------+-----+---------------------+----------------+
 */

/*
mysql> describe wp_postmeta;
+------------+-----------------+------+-----+---------+----------------+
| Field      | Type            | Null | Key | Default | Extra          |
+------------+-----------------+------+-----+---------+----------------+
| meta_id    | bigint unsigned | NO   | PRI | NULL    | auto_increment |
| post_id    | bigint unsigned | NO   | MUL | 0       |                |
| meta_key   | varchar(255)    | YES  | MUL | NULL    |                |
| meta_value | longtext        | YES  |     | NULL    |                |
+------------+-----------------+------+-----+---------+----------------+
 */

$s_sql = "SELECT DISTINCT post_title, post_content,
                 (SELECT CAST(meta_value AS SIGNED) FROM wp_postmeta WHERE wp_postmeta.meta_key = 'views' AND wp_postmeta.post_id = wp_posts.ID) AS 'views',
                 (SELECT group_concat(wp_terms.name separator ',') 
                         FROM wp_terms
                  INNER JOIN wp_term_taxonomy 
                          ON wp_terms.term_id = wp_term_taxonomy.term_id
                  INNER JOIN wp_term_relationships wpr 
                          ON wpr.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
                  WHERE 
                         taxonomy= 'category' AND wp_posts.ID = wpr.object_id
                ) AS 'Categories',
                (SELECT group_concat(wp_terms.name separator ', ') 
                        FROM wp_terms
                 INNER JOIN wp_term_taxonomy 
                         ON wp_terms.term_id = wp_term_taxonomy.term_id
                 INNER JOIN wp_term_relationships wpr 
                         ON wpr.term_taxonomy_id = wp_term_taxonomy.term_taxonomy_id
                 WHERE 
                        taxonomy= 'post_tag' AND wp_posts.ID = wpr.object_id
                ) AS 'Tags',
               ID, post_name, post_date, post_modified, post_type
          FROM wp_posts
          WHERE 
                post_type = 'post' AND post_status = 'publish'
          ORDER BY
                $s_sort";

$o_result = $o_conn->query($s_sql);

if ($o_result->num_rows > 0) {
    ?><table style="border:1px solid">
    <tr class="first"><th>Title</th><th style="min-width:100px">Views</th><th style="min-width:150px">Creation Date</th><th>Categories</th><th>Tags</th></tr>

    <?php
    $i_total_views = 0;
    $i_articles = 0;

    // output data of each row
    while($row = $o_result->fetch_assoc()) {
        $s_style='style="border:1px solid"';
        $s_style='';
        $s_url = $row['post_name'];
        print('<tr>');
        print("<td $s_style>");
        print('<a href="'.$s_url.'" target="_blank">');
        print($row["post_title"]);
        print('</a>');
        print("</td>");
        print('<td class="centered" '.$s_style.'>');
        print(number_format($row["views"]));
        print("</td>");
        print("<td $s_style>");
        print("<small>");
        print($row["post_date"]);
        print("</small>");
        print("</td>");
        print("<td $s_style>");
        $s_categories = $row["Categories"];
        $a_categories = explode (",", $s_categories);
        $s_categories_content = "";
        foreach($a_categories as $s_category) {
            $s_category_slug = "/category/".get_category_slug($s_category)."/";
            $s_categories_content = $s_categories_content .'<a href="'.$s_category_slug.'" target="_blank">';
            $s_categories_content = $s_categories_content .$s_category;
            $s_categories_content = $s_categories_content ."</a>, ";
        }

        if (strlen($s_categories_content) > 0) {
            $s_categories_content = substr($s_categories_content, 0, -2);
        }

        print($s_categories_content);
        print("</td>");
        print("<td $s_style>");
        print($row["Tags"]);
        print("</td>");
        // $row["post_content"];
        $i_total_views = $i_total_views + intval($row["views"]);
        $i_articles++;
        echo "</tr>";
    } ?></table><?php
    print("<strong>Total articles:</strong> ".number_format($i_articles)." <strong>Total Views:</strong> ".number_format($i_total_views));
    print("<br>");
} else {
    echo "<p>0 results</p>";
}
$o_conn->close();

?>
</body>
</html>

Stopping and investigating a WordPress xmlrpc.php attack

One of my Servers got heavily attacked for several days. I describe here the steps I took to stop this.

The attack consisted in several connections per second to the Server, to path /xmlrpc.php.

This is a WordPress file to control the pingback, when someone links to you.

My Server it is a small Amazon instance, a m1.small with only one core and 1,6 GB RAM, magnetic disks and that scores a discrete 203 CMIPS (my slow laptop scores 460 CMIPS).

Those massive connections caused the server to use more and more RAM, and while the xmlrpc requests were taking many seconds to reply, so more and more processes of Apache were spawned. That lead to more memory consumption, and to use all the available RAM and start using swap, with a heavy performance impact until all the memory was exhausted and the mysql processes stopped.

I saw that I was suffering an attack after the shutdown of MySql. I checked the CloudWatch Statistics from Amazon AWS and it was clear that I was receiving many -out of normal- requests. The I/O was really high too.

This statistics are from today to three days ago, look at the spikes when the attack was hitting hard and how relaxed the Server is now (plain line).

First I decided to simply rename the xmlrpc.php file as a quick solution to stop the attack but the number of http connections kept growing and then I saw very suspicious queries to the database.

Those queries, in addition to what I’ve seen in the Apache’s error log suggested me that may be the Server was hacked by a WordPress/plugin bug and that now they were trying to hide from the database’s logs. (Specially the DELETE FROM wp_useronline WHERE user_ip = the Ip of the attacker)

[Tue Aug 26 11:47:08 2014] [error] [client 94.102.49.179] Error in WordPress Database Lost connection to MySQL server during query a la consulta SELECT option_value FROM wp_options WHERE option_name = 'uninstall_plugins' LIMIT 1 feta per include('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), include_once('/plugins/captcha/captcha.php'), register_uninstall_hook, get_option
[Tue Aug 26 11:47:09 2014] [error] [client 94.102.49.179] Error in WordPress Database Lost connection to MySQL server during query a la consulta SELECT option_value FROM wp_options WHERE option_name = 'uninstall_plugins' LIMIT 1 feta per include('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), include_once('/plugins/captcha/captcha.php'), register_uninstall_hook, get_option
[Tue Aug 26 11:47:10 2014] [error] [client 94.102.49.179] Error in WordPress Database Lost connection to MySQL server during query a la consulta SELECT option_value FROM wp_options WHERE option_name = 'widget_wppp' LIMIT 1 feta per include('wp-load.php'), require_once('wp-config.php'), require_once('wp-settings.php'), do_action('plugins_loaded'), call_user_func_array, wppp_check_upgrade, get_option

The error log was very ugly.

The access log was not reassuring, as it shown many attacks like that:

94.102.49.179 - - [26/Aug/2014:10:34:58 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
94.102.49.179 - - [26/Aug/2014:10:34:59 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
127.0.0.1 - - [26/Aug/2014:10:35:09 +0000] "OPTIONS * HTTP/1.0" 200 126 "-" "Apache/2.2.22 (Ubuntu) (internal dummy connection)"
94.102.49.179 - - [26/Aug/2014:10:34:59 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
94.102.49.179 - - [26/Aug/2014:10:34:59 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
94.102.49.179 - - [26/Aug/2014:10:35:00 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"
94.102.49.179 - - [26/Aug/2014:10:34:59 +0000] "POST /xmlrpc.php HTTP/1.0" 200 598 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"

Was difficult to determine if the Server was receiving SQL injections so I wanted to be sure.

Note: The connection from 127.0.0.1 with OPTIONS is created by Apache when spawns another Apache.

As I had super fresh backups in another Server I was not afraid of the attack dropping the database.

I was a bit suspicious also because the /readme.html file mentioned that the version of WordPress is 3.6. In other installations it tells correctly that the version is the 3.9.2 and this file is updated with the auto-update. I was thinking about a possible very sophisticated trojan attack able to modify wp-includes/version.php and set fake $wp_version = ‘3.9.2’;
Later I realized that this blog had WordPress in Catalan, my native language, and discovered that the guys that do the translations forgot to update this file (in new installations it comes not updated, and so showing 3.6). I have alerted them.

In fact later I did a diff of all the files of my WordPress installation against the official WordPress 3.9.2-ca and later a did a diff between the WordPress 3.9.2-ca and the WordPress 3.9.2 (English – default), and found no differences. My Server was Ok. But at this point, at the beginning of the investigation I didn’t know that yet.

With the info I had (queries, times, attack, readme telling v. 3.6…) I balanced the possibility to be in front of something and I decided that I had an unique opportunity to discover how they do to inject those Sql, or discover if my Server was compromised and how. The bad point is that it was the same Amazon’s Server where this blog resides, and I wanted the attack to continue so I could get more information, so during two days I was recording logs and doing some investigations, so sorry if you visited my blog and database was down, or the Server was going extremely slow. I needed that info. It was worth it.

First I changed the Apache config so the massive connections impacted a bit less the Server and so I could work on it while the attack was going on.

I informed my group of Senior friends on what’s going on and two SysAdmins gave me some good suggestions on other logs to watch and on how to stop the attack, and later a Developer joined me to look at the logs and pointed possible solutions to stop the attack. But basically all of them suggested on how to block the incoming connections with iptables and to do things like reinstalling WordPress, disabling xmlrpc.php in .htaccess, changing passwords or moving wp-admin/ to another place, but the point is that I wanted to understand exactly what was going on and how.

I checked the logs, certificates, etc… and no one other than me was accessing the Server. I also double-checked the Amazon’s Firewall to be sure that no unnecessary ports were left open. Everything was Ok.

I took a look at the Apache logs for the site and all the attacks were coming from the same Ip:

94.102.49.179

It is an Ip from a dedicated Servers company called ecatel.net. I reported them the abuse to the abuse address indicated in the ripe.net database for the range.

I found that many people have complains about this provider and reports of them ignoring the requests to stop the spam use from their servers, so I decided that after my tests I will block their entire network from being able to access my sites.

All the requests shown in the access.log pointed to requests to /xmlrpc.php. It was the only path requested by the attacker so that Ip did nothing more apparently.

I added some logging to WordPress xmlrpc.php file:

if ($_SERVER['REMOTE_ADDR'] == '94.102.49.179') {
    error_log('XML POST: '.serialize($_POST));
    error_log('XML GET: '.serialize($_GET));
    error_log('XML REQUEST: '.serialize($_REQUEST));
    error_log('XML SERVER: '.serialize($_SERVER));
    error_log('XML FILES: '.serialize($_FILES));
    error_log('XML ENV: '.serialize($_ENV));
    error_log('XML RAW: '.$HTTP_RAW_POST_DATA);
    error_log('XML ALL_HEADERS: '.serialize(getallheaders()));
}

This was the result, it is always the same:

[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML POST: a:0:{}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML GET: a:0:{}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML REQUEST: a:0:{}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML SERVER: a:24:{s:9:"HTTP_HOST";s:24:"barcelona.afterstart.com";s:12:"CONTENT_TYPE";s:8:"text/xml";s:14:"CONTENT_LENGTH";s:3:"287";s:15:"HTTP_USER_AGENT";s:50:"Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)";s:15:"HTTP_CONNECTION";s:5:"close";s:4:"PATH";s:28:"/usr/local/bin:/usr/bin:/bin";s:16:"SERVER_SIGNATURE";s:85:"<address>Apache/2.2.22 (Ubuntu) Server at barcelona.afterstart.com Port 80</address>\n";s:15:"SERVER_SOFTWARE";s:22:"Apache/2.2.22 (Ubuntu)";s:11:"SERVER_NAME";s:24:"barcelona.afterstart.com";s:11:"SERVER_ADDR";s:14:"[this-is-removed]";s:11:"SERVER_PORT";s:2:"80";s:11:"REMOTE_ADDR";s:13:"94.102.49.179";s:13:"DOCUMENT_ROOT";s:29:"/var/www/barcelona.afterstart.com";s:12:"SERVER_ADMIN";s:19:"webmaster@localhost";s:15:"SCRIPT_FILENAME";s:40:"/var/www/barcelona.afterstart.com/xmlrpc.php";s:11:"REMOTE_PORT";s:5:"40225";s:17:"GATEWAY_INTERFACE";s:7:"CGI/1.1";s:15:"SERVER_PROTOCOL";s:8:"HTTP/1.0";s:14:"REQUEST_METHOD";s:4:"POST";s:12:"QUERY_STRING";s:0:"";s:11:"REQUEST_URI";s:11:"/xmlrpc.php";s:11:"SCRIPT_NAME";s:11:"/xmlrpc.php";s:8:"PHP_SELF";s:11:"/xmlrpc.php";s:12:"REQUEST_TIME";i:1409338974;}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML FILES: a:0:{}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML ENV: a:0:{}
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML RAW: <?xmlversion="1.0"?><methodCall><methodName>pingback.ping</methodName><params><param><value><string>http://seretil.me/</string></value></param><param><value><string>http://barcelona.afterstart.com/2013/09/27/afterstart-barcelona-2013-09-26/</string></value></param></params></methodCall>
[Fri Aug 29 19:02:54 2014] [error] [client 94.102.49.179] XML ALL_HEADERS: a:5:{s:4:"Host";s:24:"barcelona.afterstart.com";s:12:"Content-type";s:8:"text/xml";s:14:"Content-length";s:3:"287";s:10:"User-agent";s:50:"Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)";s:10:"Connection";s:5:"close";}

So nothing in $_POST, nothing in $_GET, nothing in $_REQUEST, nothing in $_SERVER, no files submitted, but a text/xml Posted (that was logged by storing: $HTTP_RAW_POST_DATA):

<?xmlversion="1.0"?><methodCall><methodName>pingback.ping</methodName><params><param><value><string>http://seretil.me/</string></value></param><param><value><string>http://barcelona.afterstart.com/2013/09/27/afterstart-barcelona-2013-09-26/</string></value></param></params></methodCall>

I show you in a nicer formatted aspect:So basically they were trying to register a link to seretil dot me.

I tried and this page, hosted in CloudFare, is not working.

The problem is that responding to this spam xmlrpc request took around 16 seconds to the Server. And I was receiving several each second.

I granted access to my Ip only on the port 80 in the Firewall, restarted Apache, restarted MySql and submitted the same malicious request to the Server, and it even took 16 seconds in all my tests:

cat http_post.txt | nc barcelona.afterstart.com 80

I checked and confirmed that the logs from the attacker were showing the same Content-Length and http code.

Other guys tried xml request as well but did one time or two and leaved.

The problem was that this robot was, and still sending many requests per second for days.

May be the idea was to knock down my Server, but I doubted it as the address selected is the blog of one Social Event for Senior Internet Talents that I organize: afterstart.com. It has not special interest, I do not see a political, hateful or other motivation to attack the blog from this project.

Ok, at this point it was clear that the Ip address was a robot, probably running from an infected or hacked Server, and was trying to publish a Spam link to a site (that was down). I had to clarify those strange queries in the logs.

I reviewed the WPUsersOnline plugin and I saw that the strange queries (and inefficient) that I saw belonged to WPUsersOnline plugin.

The thing was that when I renamed the xmlrpc.php the spamrobot was still posting to that file. According to WordPress .htaccess file any file that is not found on the filesystem is redirected to index.php.

So what was happening is that all the massive requests sent to xmlrpc.php were being attended by index.php, then showing an error message that page not found, but the WPUsersOnline plugin was deleting those connections. And was doing it many times, overloading also the Database.

Also I was able to reproduce the behaviour by myself, isolating by firewalling the WebServer from other Ips other than mine and doing the same post by myself many times per second.

I checked against a friend’s blog but in his Server xmlrpc.php responds in 1,5 seconds. My friend’s Server is a Digital Ocean Virtual Server with 2 cores and SSD Disks. My magnetic disks on Amazon only bring around 40 MB/second. I’ve to check in detail why my friend’s Server responds so much faster.

Checked the integrity of my databases, just in case, and were perfect. Nothing estrange with collations and the only errors in the /var/log/mysql/error.log was due to MySql crashing when the Server ran out of memory.

Rechecked in my Server, now it takes 12 seconds.

I disabled 80% of the plugins but the times were the same. The Statistics show how the things changed -see the spikes before I definitively patched the Server to block request from that Spam-robot ip, to the left-.

I checked against another WordPress that I have in the same Server and it only takes 1,5 seconds to reply. So I decided to continue investigating why this WordPress took so long to reply.

As I said before I checked that the files from my WordPress installation were the same as the original distribution, and they were. Having discarded different files the thing had to be in the database.

Even when I checked the MySql it told me that all the tables were OK, having seen that the WPUserOnline deletes all the registers older than 5 minutes, I guessed that this could lead to fragmentation, so I decided to do OPTIMIZE TABLE on all the tables of the database for the WordPress failing, with InnoDb it is basically recreating the Tables and the Indexes.

I tried then the call via RPC and my Server replied in three seconds. Much better.

Looking with htop, when I call the xmlrpc.php the CPU uses between 50% and 100%.

I checked the logs and the robot was gone. He leaved or the provider finally blocked the Server. I don’t know.

Everything became clear, it was nothing more than a sort of coincidences together. Deactivating the plugin the DELETE queries disappeared, even under heavy load of the Server.

It only was remain to clarify why when I send a call to xmlrpc to this blog, it replies in 1,5 seconds, and when I request to the Barcelona.afterstart.com it takes 3 seconds.

I activated the log of queries in mysql. To do that edit /etc/mysql/my.cnf and uncomment:

general_log_file        = /var/log/mysql/mysql.log
general_log             = 1

Then I checked the queries, and in the case of my blog it performs many less queries, as I was requesting to pingback to an url that was not existing, and WordPress does this query:

SELECT   wp_posts.* FROM wp_posts  WHERE 1=1  AND ( ( YEAR( post_date ) = 2013 AND MONTH( post_date ) = 9 AND DAYOFMONTH( post_date ) = 27 ) ) AND wp_posts.post_name = 'afterstart-barcelona-2013-09-26-meet' AND wp_posts.post_type = 'post'  ORDER BY wp_posts.post_date DESC

As the url afterstart-barcelona-2013-09-26-meet with the dates indicated does not exist in my other blog, the execution ends there and does not perform the rest of the queries, that in the case of Afterstart blog were:

40 Query     SELECT post_id, meta_key, meta_value FROM wp_postmeta WHERE post_id IN (81) ORDER BY meta_id ASC
40 Query     SELECT ID, post_name, post_parent, post_type
FROM wp_posts
WHERE post_name IN ('http%3a','','seretil-me')
AND post_type IN ('page','attachment')
40 Query     SELECT   wp_posts.* FROM wp_posts  WHERE 1=1  AND (wp_posts.ID = '0') AND wp_posts.post_type = 'page'  ORDER BY wp_posts.post_date DESC
40 Query     SELECT * FROM wp_comments WHERE comment_post_ID = 81 AND comment_author_url = 'http://seretil.me/'

To confirm my theory I tried the request to my blog, with a valid url, and it lasted for 3-4 seconds, the same than Afterstart’s blog. Finally I double-checked with the blog of my friend and was slower than before. I got between 1,5 and 6 seconds, with a lot of 2 seconds response. (he has PHP 5.5 and OpCache that improves a bit, but the problem is in the queries to the database)

Honestly, the guys creating WordPress should cache this queries instead of performing 20 live queries, that are always the same, before returning the error message. Using Cache Lite or Stash, or creating an InMemory table for using as Cache, or of course allowing the use of Memcached would eradicate the DoS component of this kind of attacks. As the xmlrpc pingback feature hits the database with a lot of queries to end not allowing the publishing.

While I was finishing those tests (remember that the attacker ip has gone) another attacker from the same network tried, but I had patched the Server to ignore it:

94.102.52.157 - - [31/Aug/2014:02:06:16 +0000] "POST /xmlrpc.php HTTP/1.0" 200 189 "-" "Mozilla/4.0 (compatible: MSIE 7.0; Windows NT 6.0)"

This was trying to get a link published to a domain called socksland dot net that is a domain registered in Russia and which page is not working.

As I had all the information I wanted I finally blocked the network from the provider to access my Server ever again.

Unfortunatelly Amazon’s Firewall does not allow to block a certain Ip or range.
So you can block at Iptables level or in .htaccess file or in the code.
I do not recommend blocking at code level because sadly WordPress has many files accessible from outside so you would have to add your code at the beginning of all the files and because when there is a WordPress version update you’ll loss all your customizations.
But I recommend proceeding to patch your code to avoid certain Ip’s if you use a CDN. As the POST will be sent directly to your Server, and the Ip’s are Ip’s from the CDN -and you can’t block them-. You have to look at the Header: X-Forwarded-For that indicates the Ip’s the proxies have passed by, and also the Client’s Ip.

I designed a program that is able to patch any PHP project to check for blacklisted Ip’s (even though a proxy) with minimal performance impact. It works with WordPress, drupal, joomla, ezpublish and Framework like Zend, Symfony, Catalonia… and I patched my code to block those unwanted robot’s requests.

A solution that will work for you probably is to disable the pingback functionality, there are several plugins that do that. Disabling completely xmlrpc is not recommended as WordPress uses it for several things (JetPack, mobile, validation…)

The same effect as adding the plugin that disables the xmlrpc pingback can be achieved by editing the functions.php from your Theme and adding:

add_filter( 'xmlrpc_methods', 'remove_xmlrpc_pingback_ping' );
function remove_xmlrpc_pingback_ping( $methods ) {
    unset( $methods['pingback.ping'] );
    
    return $methods;
}

Update: 2016-02-24 14:40 CEST
I got also a heavy dictionary attack against wp-login.php .Despite having a Captcha plugin, that makes it hard to hack, it was generating some load on the system.
What I did was to rename the wp-login.php to another name, like wp-login-carles.php and in wp-login.php having a simply exit();

<?php
exit();

Take in count that this will work only until WordPress is updated to the next version. Then you have to reapply the renaming trick.