Distributed Denial of Service (DDoS) attacks are becoming a common trend on our blog lately, and that’s okay because it’s a very serious issue for every website owner. Today I want to talk about a large DDoS attack that leveraged thousands of unsuspecting WordPress websites as indirect source amplification vectors.
Any WordPress site with pingback enabled (which is on by default) can be used in DDOS attacks against other sites. Note that XMLRPC is used for pingbacks, trackbacks, remote access via mobile devices and many other features you’re likely very fond of. But, it can also be heavily misused like what we are seeing.
The Story
It all happened against a popular WordPress site that had gone down for many hours due to a DDoS. As the attack increased in size, their host shut them down and then they decided to ask for help. They subscribed to our Website Firewall.
Once the DNS was ported over, we were able to see what was going on. It was a large HTTP-based (layer 7) distributed flood attack, sending hundreds of requests per second to their server. The requests looked like this:
74.86.132.186 - - [09/Mar/2014:11:05:27 -0400] "GET /?4137049=6431829 HTTP/1.0" 403 0 "-" "WordPress/3.8; http://www.mtbgearreview.com" 121.127.254.2 - - [09/Mar/2014:11:05:27 -0400] "GET /?4758117=5073922 HTTP/1.0" 403 0 "-" "WordPress/3.4.2; http://www.kschunvmo.com" 217.160.253.21 - - [09/Mar/2014:11:05:27 -0400] "GET /?7190851=6824134 HTTP/1.0" 403 0 "-" "WordPress/3.8.1; http://www.intoxzone.fr" 193.197.34.216 - - [09/Mar/2014:11:05:27 -0400] "GET /?3162504=9747583 HTTP/1.0" 403 0 "-" "WordPress/2.9.2; http://www.verwaltungmodern.de" ..
If you notice, all queries had a random value (like “?4137049=643182“) that bypassed their cache and force a full page reload every single time. It was killing their server pretty quickly.
But the most interesting part is that all the requests were coming from valid and legitimate WordPress sites. Yes, other WordPress sites were sending that random requests at a very large scale and bringing the site down.
WordPress Insecure Default Option = Very Large Botnet
Just in the course of a few hours, over 162,000 different and legitimate WordPress sites tried to attack his site. We would likely have detected a lot more sites, but we decided we had seen enough and blocked the requests at the edge firewall, mostly to avoid filling the logs with junk.
Can you see how powerful this can be? One attacker can use thousands of popular and clean WordPress sites to perform their DDOS attack while being hidden in the shadows. That all happens with a simple pingback request to the XML-RPC file:
$ curl -D - "www.anywordpresssite.com/xmlrpc.php" -d '<methodCall><methodName>pingback.ping</methodName><params><param><value><string>http://victim.com</string></value></param><param><value><string>www.anywordpresssite.com/postchosen</string></value></param></params></methodCall>'
Yes, that simple command on Linux can start it all.
Is Your Site Attacking Others?
It might be, and you could have no idea. To verify, look through your logs for any POST requests to the XML-RPC file, similar to the one below. If you see a pingback to a random URL, you know your site is being abused.
93.174.93.72 - - [09/Mar/2014:20:11:34 -0400] "POST /xmlrpc.php HTTP/1.0" 403 4034 "-" "-" "POSTREQUEST:<?xml version=x221.0x22 encoding=x22iso-8859-1x22?>x0A<methodCall>x0A<methodName>pingback.ping</methodName>x0A<params>x0A <param>x0A <value>x0A <string>http://fastbet99.com/?1698491=8940641</string>x0A </value>x0A </param>x0A <param>x0A <value>x0A <string>yoursite.com</string>x0A </value>x0A </param>x0A</params>x0A</methodCall>x0A" 94.102.63.238 – - [09/Mar/2014:23:21:01 -0400] "POST /xmlrpc.php HTTP/1.0" 403 4034 "-" "-" "POSTREQUEST:x0Ax0Apingback.pingx0Ax0Ax0A x0A http://www.guttercleanerlondon.co.uk/?7964015=3863899x0A x0A x0Ax0A x0A yoursite.comx0A x0A x0Ax0Ax0A"
In these cases someone tried to use one of our honeypots to DDoS fastbet99.com and guttercleanerlondon.co.uk (we don’t know or service these websites).
Prevent XML-RPC Abuse
To stop your WordPress website from being misused, you will need to disable the XML-RPC (pingback) functionality on your site.
You can do this by removing the file, xmlrpc.php, or you can disable notifications in your settings. The biggest challenge you’ll find with removing the file is that on an update it’ll come right back, annoying, I know. Some preliminary tests are showing that we’re able to bypass the disable notification setting but we are still investigating.
Update: A better way to block it is by creating a plugin that adds the following filter:
add_filter( ‘xmlrpc_methods’, function( $methods ) {
unset( $methods[‘pingback.ping’] );
return $methods;
} );
This is a well known issue within WordPress and the core team is aware of it. It’s not something that will be patched though. In many cases this same issue is categorized as a feature, one that many plugins use, so in therein lies the dilemma.
Online Tool to Check if Your Site Was Misused
Because of how prevalent an issue this is becoming, we’ve put together a little scanner that will check if your website has shown up in our logs. This scanner is only looking to see if your site has used to attack anyone within our network.
Use our WordPress DDOS Scanner to check if your site is DDOS’ing other websites.
Try it out and do your part to make the Internet a safer place for everyone.
Victor Santoyo
Matt Morrow![Malware comes in many different varieties. Analyst Krasimir Konov is on this month’s Sucuri Sit-Down to help keep them all straight. From malicious iframes to SEO spam, join host Justin Channell as he racks Krasimir’s brain on all the different types of malware. Also, Krasimir discusses his recent blog post about a malicious cURL downloader, and Justin breaks down the latest website security news, including patched plugins you should update. Podcast Transcript Justin Channell: Hello, and welcome to the Sucuri Sit Down. I'm your host, Justin Channell, and this is a monthly podcast about website security, where we get in-depth with the malware removal experts here at Sucuri. Later in the show, I'll have our analyst Krasimir Konov to chat about some different types of malware, but first, let's take a look at other topics we've published on our blog and Sucuri labs notes this month. First up, we have some new information about credit card skimming with hackers using a hybrid method to steal payment information from eCommerce websites. Our analyst Dennis Sinegubko wrote about this for the Sucuri blog back at the beginning of June. Now, most credit card stealing malware is a client side JavaScript that grabs data and sends it to a third party server. But, that approach has a drawback for bad actors because it's still possible to track the requests and catch them as being suspicious. Now, to get around that, bad actors have started harvesting information server side by modifying core PHP files. In this case, the infection would be undetectable from the outside, but it's still going to be pretty easy to find because you're rarely modifying any of those core files, so any of those changes that are going to come up are going to be suspicious. To get around both of these drawbacks, we're seeing bad actors combine the two. So client side snippets of JavaScript are sending stolen credit card data to server side scripts that they've installed on the same server as the site. Now, this allows bad actors to cover their tracks a little bit because the traffic that's being redirected is going to the same server, and that's less likely to be flagged as suspicious. It's a bit more complicated to pull this off, but our team has been seeing this hybrid approach in the wild, so it's something to be on the lookout for. Now, another month has passed, and we found more cross site scripting attacks targeting WordPress plugins. Most notably, we discovered one that affects users of the YITH WooCommerce Ajax Product Filter plugin. Now, this is a plugin that allows WooCommerce stores to be filtered by product type, and it's pretty popular. It's got about 100,000 users right now, so with it being vulnerable, it's very important that all of them update to the latest version, which is 3.11.1. Some of the other plugins we found cross site scripting vulnerabilities with included Elementor Page Builder, Careerfy, JobSearch, and Newspaper. If you're looking for a full list of vulnerabilities that have been patched this month, John Castro at the Sucuri Labs blog has you covered. Check out our show notes for the link. Also, this month I had a blog go up detailing what's called a jibberish hack. It's basically the same motivation as an SEO spam attack where bad actors use your site's good standing to redirect visitors to their own sites. But in this attack, you'll find a bunch of randomly named folders filled with a ton of HTML files with really nonsensical file names like cheap-cool-hairstyles-photos.html. It's just going to be a mishmash of keywords that clearly you didn't put there. Unfortunately, just deleting all those HTML files and folders is not going to be enough to get rid of that jibberish hack though. You're going to need to fully clean any hacked files and database tables, and then you're going to have to deal with all the damage caused to your site's standing. And just keep in mind, if you find anything about that process too daunting, we're always here to help. Now, for this month's Sit Down, we have Sucuri analyst Krasimir Konov. Earlier in June, he had written a lab's note about a malicious downloader script that used the curl function, and we chatted a bit about it, but more importantly, we went really in-depth on all the different varieties of malware that website owners need to be aware of. But, before I get started with Krasimir, I just wanted to remind you about the Sucuri Sync-Up, our sister podcast. It's a weekly website security news briefing that you can find anywhere you get your podcasts, as well as the video version on our social media feed, and now you can even get it on your Amazon Alexa smart speakers. Just search Amazon skills for Sucuri Sync-Up, add the flash briefing, and get new content delivered every Monday. Now, on with the show. Hi Krasimir, thanks for joining us on the show. I thought we could start off and maybe have you tell us a little bit about yourself and what you do here at Sucuri? Krasimir Konov: Yeah, sure. Well, I joined Sucuri originally in 2014, but I've been in the IT business for about 10 years. Nine of those I did security. And currently at Sucuri I'm one of the malware analysts. I used to work in the front lines, used to clean websites and whatnot, and then I gradually moved up, and now I'm working in the malware research department. And my day to day job is basically analyzing malware, and then once I analyze it and figure out what it is, then I will create a signature for it. And we'll add those signatures to our tools, so we can automate some of the work we do. And I also write some Labs Notes blog posts. Usually, if I find something interesting in malware or some security topic, I'll write about it. Justin Channell: Yeah. And of those topics recently that you wrote about, one was about a malicious curl downloader, and how exactly did that work? Krasimir Konov: Right, yeah. That was an interesting one, but not very unique or anything like that. We see that a lot with curl being used as a downloader. It's a very common malware. So rather than including the actual malware in the file, the attackers would use curl to download the malicious code. In this case, they'll download it from Pastebin, but it could be anything. It could be another website or anything like that, and curl would just make a call to the website, request the code. The website will respond with the code, and then later on, there is some code to either save the output somewhere on the website, or you'll just run it through eval and execute the actual code right away. Justin Channell: Right. And you said that it's commonly found in malware, but let's kind of maybe talk a bit broader about malware in general. What is everything that is classified as malware? Krasimir Konov: Well, in general it will be anything that the owner of the website didn't authorize, anything that was added by a third party. There is a lot of different malware. It could be even something like a defacement that will also be considered malware because it was something the user did not authorize. Even though it might not be doing anything malicious on the website, it's not infecting users, the visit is still something they did not authorize. So defacement would also be considered malware. And even something like ransomware where the website is technically not really damaged, it's all encrypted, but it's not infecting anybody. It's not doing anything malicious, but it's still encrypting the entire website and asking the user or the customer, the owner of the website for a ransom they need to pay in order to get the website back online. Justin Channell: Okay. Let's maybe break it down to each individual type of malware. For example, what would be a way that maybe I-frames could be maliciously used by a hacker? Krasimir Konov: Yeah. An I-frame can be used maliciously when it loads content from another location. You can look at the I-frame as a window that just opens another website. So anything that website has on it, you're pretty much loading it through the I-frame. So if that website is infected and it's serving some kind of malware, by opening an I-frame, you're loading all those elements, everything that was on this website. And sometimes the I-frame can be as small as pixel or something hidden somewhere off the screen, so you wouldn't even know that it was opening it. Justin Channell: And yeah, I feel like we've also seen a lot of them where they're used almost to mimic popups as well. Krasimir Konov: Yeah. I mean the I-frame, it could just load from another website and the other website could do anything. It could be serving just malware and it would try to infect the user that doesn't even know that they're being connected to the other website. It could just have some other JavaScript that's just trying to open up pop ups on the original website through the I-frame. Yeah, it could be a lot of things. Justin Channell: Okay. And also, let's talk a little bit about conditional redirects and how those work. What allows a script to detect which devices are coming in and where they're coming from? Krasimir Konov: Right. Yeah. That's a common one we see a lot. Basically, a conditional redirect would be something, it's a redirect on the website. It's obviously malicious, but there's certain conditions that need to be met before the redirect is actually executed or the redirect happens. For example, let's say if it's on a phishing website or a phishing page that is hidden somewhere on the website. For example, if Google visits it, obviously the attacker doesn't want Google to see the actual phishing page and record it as a phishing page. So they'll look for, for example, the IP address. They would look for the user agent. And a lot of times they can tell that it's a bot. So they'll just return a 404 response, for example, that will be like, "Oh, page not found." So Google would be like, "Oh, it looks like this page doesn't exist." But then if a regular user goes to the same page, then those conditions will be met. The actual website or the script behind the phishing will check and see, and be like, "Oh, this one is running Firefox or Chrome," and be like, okay. And then they'll look at the IP and be like, "Oh, he's in whatever, he's in United States somewhere." And he's like, "Oh, okay. That's good." And then once all of these conditions are met, then the actual script will serve them the actual phishing page. And it'll be like, "Oh, you need to fill out this to recover your account or whatever, or type in your credentials to log in here." Justin Channell: And so this is the type of thing we're really, a website owner is going to run into this more commonly when people are complaining about they're getting served bad content or whatever, and they can't seem to replicate it. It's likely probably these kind of redirects. Is that right? Krasimir Konov: Right, right. It could be something as specific as, for example, a range of IP addresses that correspond to an ISP or maybe let's say a country. It could be like, "Oh, were targeting only customers in the US," so if you're connecting from another country and you go to the same website or the same page, it would just say 404. It will give you a page not found. But then if you actually have an IP address from the United States, you're connecting from the United States, then it will actually show you the phishing page. Justin Channell: Now another type of malware I feel like we see a lot here is SEO spam. We hear people talking about that. What are some of the top SEO spam keywords that you see coming through? Krasimir Konov: Yeah. We get that a lot. We see a lot of spam on websites. A lot of times attackers will use SEO spam to gain ranking for their own website. Or they'll just try to include some kind of SEO spam in links to another website that they're currently running or something. I mean, these things change all the time. So a website might be up for a week and then it'll disappear, and then they'll start another campaign. But yeah, we see that a lot. We see all kinds of keywords they use. Most common ones will be something like Viagra. We'll have like jerseys for sale. A lot of times, they'll use name brands like Nike, Rolex, Prada. We've seen even some essay writing services for some reason. I'm not sure why, but that's common. We see, for example, pharmaceuticals a lot that will use specific medicine names. They'll use all kinds of replicas, like a replica bag of this, replica this, replica that. We'd see prescription, also payday loans. And obviously there's some adult related sites and things like that keywords. Justin Channell: So pretty much anything that people are going to be searching and clicking on are probably going to be targets for SEO spam? Krasimir Konov: Right. I think a lot of it commonly is pharma related because a lot of people are looking to buy medicine online, and a lot of times will require a prescription. So a lot of people are like, "Oh, let me see if I can find this medicine that I can buy it online somewhere." They don't need a prescription. They don't want to pay to visit a doctor and whatnot, and they'll look for it. And yeah. Justin Channell: Now, whenever somebody's website does get hacked with a SEO spam attack, what kind of effect can it have on the website beyond just being defaced? Krasimir Konov: Yeah. You can have a lot of things can happen, negative things. For example, the website can be blacklisted because of the keywords. And that usually represents a big red warning when you go on the website, depending on who blacklisted it. But if it's Google, for example, you'll see a big warning and it'll tell you this website contains malware or there's something wrong with this website. So, pretty much all the traffic on the website will be gone. And then you can also lose a lot of your reputation if there is a SEO spam on the website. For example, if you were ranked in say number five for certain keywords that represent your product on Google search engines, and then suddenly you get hit with SEO spam, then all these search engines then go and visit the website. And all of a sudden they're like, "Oh, there's all these weird key words on here, all this SEO spam that's causing a lot of mixed signals." And the search engines are like, "Oh, where do we rank this website now? Do we rank them with this product that's originally what the website is about? Or do we take into consideration all these other keywords that are mixed up that are SEO spam?" So, all of a sudden your website might go from being ranked number five on the first page to being on the 10th page. And then you rank for all these other keywords that you didn't intend to. And then people search for something completely different. They're searching for jerseys or something, or now they're searching for Prada products, and then suddenly your website pops up in there. So you're not really getting any good traffic, not targeted traffic. But, yeah. Justin Channell: Okay. So in a lot of ways, the effects of SEO spam would kind of be the same for defacements or any kind of malware with the blacklisting, but it does bring that kind of unique part to it where then it can also then bring traffic that you weren't expecting from somebody searching for jerseys, for example. I had not really ever thought about that. Krasimir Konov: Right, right. Yeah. It will definitely bring some traffic. I've seen a lot of times where websites will be connected. Let's say, there was 1,000 websites that were all infected with SEO spam, and it will kind of link each other to try to bring each other up into the rankings. And so you would see a lot of strange traffic from some random websites that were, for example, that were previously infected, even if they might not be anymore. But yeah, they'll be sending traffic to you or there'll be usually search engines sending you traffic, but for the wrong keywords. People are looking for something else, so obviously they're not going to be interested in your website. They're not going to buy anything because they're not looking for that. Justin Channell: And now, so thinking of the way websites get infected, a very common way it seems to be is through phishing campaigns. What are some recommendations you have for the best ways to avoid becoming a phishing victim? Krasimir Konov: Yeah. There is some ways. I mean, it depends really on the type of attack. Obviously, a lot of people, when they think of phishing, they think, "Oh, it's just like a PayPal phishing page and it just looks like the original," but it could be more subtle. If it's just a regular page where you're just going and you get redirected to another website, obviously the first thing to look is if you have the security padlocks, make sure that traffic is encrypted. A lot of these websites don't really have any encryption nowadays. More are starting to get that with pre SSLs being issued and whatnot. But that's the first thing to look and see, make sure. Anywhere you're typing your sensitive information, you want to make sure you have the padlock to make sure everything is encrypted. Krasimir Konov: But also you want to look at the URL of the actual website you're visiting. A lot of times they'll try to hide it. So you might have to be careful and look closely. Something that might be an I will be an L or something like that. And a capital I and L might look kind of similar into your IRL, so you might miss something like that. Say, if you're looking for PayPal and it might replace the L with an I, and if you don't look closely, it might look exactly the same. And you're like, "Oh, okay, it's paypal.com," but not really. So yeah. Just pay attention to the URL, make sure it is the actual website. There's no paypal.com dot something, dot something else, dot com. Yeah. You want it to just say paypal.com, and then it'll have forward slash and something else. But yeah, it gets more complicated when you have, for example, a phishing page that's injected into a regular page. For example, you have a checkout page on a website that you're buying things from and you go through the checkout page and you're looking at where you type in your credit card information and whatnot. And you might have a phishing page that actually looks exactly like a little box that gives you where you put in your credit card number, or your name, your address, and all that. So that will be more subtle. For example, that could be also an I-frame that's just coming from another page. And it will look exactly like it's part of the website. You're on the legitimate website, but only that portion of the website is actually the phishing page. And you look at it and you're like, "Oh, okay. It looks fine. I'm just putting my credentials." So that one could be a lot harder to figure it out. Usually, if it's something like that, I look for something that looks kind of out of place. Maybe they didn't get the right font. It might not be the same as the original website or there might be something out of place, some fields that are missing or some fields that are squished into the left or the right. It looks kind of awkward. It's like, why would this be like this? The whole website looks professional. There's a pink background or something, for example, and then suddenly there's this white box in the middle. It's like, ah, it looks kind of weird, out of place. Justin Channell: So pretty much if anything looks slightly out of place, you really should double check everything at that point. Krasimir Konov: Right. Right. Yeah. Obviously there's more ways that you can check, but I wouldn't get into more technical, like inspecting elements and looking at stuff, but yeah. Justin Channell: And now another type of malware that's kind of, and it kind of plays in with whatever the other infection is, is backdoors. Can you give us some examples of what backdoors can be? It's mainly just when a hacker can get back into the site to reinfect it, but I know there are a ton of different methods. And what are some of the more common ones and then maybe some that really interesting that you've seen? Krasimir Konov: Yeah, there is a lot. They'll probably be one of the first things the hacker would do is if they compromise a website, obviously they'll try to spread backdoors and just inject code everywhere so they can get back in, even if the owner of the website or webmaster cleans it. They want to try and hide some malicious code somewhere so they can always get back in. There's many variations. A backdoor could be something as simple as a single line of code to just [inaudible 00:20:19] argument, some kind of string or something via get or post. Krasimir Konov: And then it runs into an eval, so it evaluates the code and executes it. And some backdoors are very complex and they can be included in, let's say you have a WordPress site and you have a specific login page where all the login credentials are being processed and everything else. They could even inject code into that to basically bypass the whole login mechanism so that they can just bypass everything. They don't even have to know any user. They don't have to know the password, nothing. They'll just include some lines in there, and every time they'll be just able to log in. Yeah. It gets pretty crazy. Yeah. I mean, there's all kinds of malware. There is always a malware, for example, that just targets credit cards and will just target the eCommerce websites. And they'll just try to steal the login credentials, I mean, the credit cards. They'll try to get your address, your credit card information, any kind of CVV code or whatever you typed into the billing address, everything. And then there's also malware like the backdoors that are just trying to keep the attacker in control and trying to get them back into the website. There's just so many variations of what a malicious user might want to do on a website. Some can be something as simple as just reinfecting the website. They don't want to keep control. They just want to keep reinfecting it with some kind of malware. So even if you clean it, it would just get reinfected. Some of them in the database, otherwise might be in the files. We've seen some added into a [inaudible 00:22:14] job that just keeps running on the server. There could be malware that is just a giant to, for example, attack out of websites. Like for example, a distributed denial service where they put the same malware on thousands of websites. And then they try to send traffic to one website to try to bring it down. Yeah. People try to do all kinds of stuff with websites. We've seen even some cryptocurrency mining malware that you go onto a website and suddenly your PC starts running like crazy. And you're like, what the hell is going on? Your fans turn on and the PC is 100% CPU. And it turns out that the website has some malware that's just by mining Bitcoins with your CPU and it's using all of it. Justin Channell: Wow. Okay. So one question now, the last question I have is of all the malware that you've seen, what do you think is the coolest piece of malware that you've ever seen? Krasimir Konov: I think the coolest would be the ones that are so subtle that you don't even know that it's there. For example, we've seen some that were pretty innovative. It will be just a one liner code that's just one line. And for example, it will be let's say 40-50 characters, something like that. And that's all it is. And they'll hide it somewhere in between the legitimate code. And if you don't know what you're looking for, you would never see it. It doesn't look suspicious. There is no links to some other website. There's no some kind of encrypted code or anything like that. It's just a simple one line. And then if you're just scrolling through the file looking for something, you would never see it. It just looks like all the other code. And then if you look closely, you're like, "Oh, there's this..." Look closely, and you're like, "Oh wow, this is not supposed to be there." And then you keep looking at it and you're like, "This looks really weird." And then you see that it's actually doing some malicious things and trying to evaluate some code or taking output from the outside, I mean, some input from outside, you can call it and give it code to run. Justin Channell: Well, Krasimir, thanks for coming on and talking to us for today. Krasimir Konov: Yeah. Thank you. Thank you. I'm so happy. I'm glad I was able to do this podcast and I can't wait to do another one. Justin Channell: Yeah, we'll have you on again. Thanks. Krasimir Konov: Thank you. Justin Channell: Thanks again to Krasimir for joining us here on the Sit Down. We'll be back with another episode next month. So be sure to subscribe on Apple podcasts, Spotify, Stitcher, or any podcasting platform. Also, be sure to follow us on social media at Sucuri Security and check us out at sucuri.net. That's S-U-C-U-R-I.net. I'm Justin Channell, And this has been the Sucuri Sit Down. Stay safe out there.](https://blog.sucuri.net/wp-content/uploads/2020/05/20-sucuri-podcast-blog-post_blog_image-390x183.jpg)
Justin Channell
Art Martori
Denis Sinegubko
Sucuri Malware Research Team
Cesar Anjos
Ashley Sand
Bruno Zanelato
48 comments
Very interesting! Thank you for this.
How will this affect (or not) the JetPack plugin ?
It will prevent Jetpack from functioning, as you’re hacking core — which is always a bad idea.
What you should do, is `add_filter(‘xmlrpc_enabled’,’__return_false’);` or install http://wordpress.org/plugins/disable-xml-rpc/ instead.
Hello. I see a lot of executions in one of our sites. How can I tell which ones are from JetPack servers?
Can anyone confirm if the plugin Disable XML-RPC may negatively effect JetPack functions?
If you use stats module, you need XML-RPC enabled.
But you don’t need to turn off entire XML-RPC, you can turn off only pingbacks. If you don’t want to mess with code, simply install and activate this plugin http://wordpress.org/plugins/disable-xml-rpc-pingback/
Also, to check if the plugin is working, you can test XML-RPC remotely from http://xmlrpc.eritreo.it/
You could do something very simple that just disables Pingbacks and not all of XML-RPC. Something like this should work ( not tested ):
add_action( ‘xmlrpc_call’, function( $method ) {
if ( $method === ‘pingback.ping’ ) {
wp_die( ‘No pingbacks’, ‘Pingback is disabled’, array( ‘response’ => 403 ) );
}
} );
There should be no need to hack core WordPress or disable all of XML-RPC.
It looks to me like add_filter(‘xmlrpc_enabled’,’__return_false’) does NOT prevent pingbacks in wp 3.8.1, it’s only checked in wp_xmlrpc_server::login, which isn’t used for pingbacks.
‘xmlrpc_call’ is checked for pingbacks.
I agree with George in his reply, you should not hack core and that wasn’t the intention of mentioning that. Our solution to disabling XML-RPC was adding the option in CloudProxy, our website firewall.
XML-RPC is required in JetPack to auth with WordPress.com so if you disable XML-RPC, you will get a connection error when attempting to authenticate.
We actually use it after the initial authentication as well, for the ongoing two-way communication between WPCOM servers and the Jetpack site — for example, asynchronously pulling posts up into our elasticsearch index if the site has Related Posts turned on, for the WPCOM REST API module, and others.
(just to specify that temporarily unblocking it for authorization and then reblocking can still have bad side effects)
(if you’d like details on IP ranges that Jetpack requests may come in from to whitelist, just drop me a line on Skype — same as my Twitter handle)
We’ve identified the source of the pingbacks, and we’re looking to see if the Akismet plugin can help to prevent it.
That would be awesome. Any luck there?
As far as I am concerned you fail to explain the amplification. If it’s not amplified, I see no reason why I should care.
Just wondering if unchecking the “Attempt to notify any blogs linked to from the article” &
“Allow link notifications from other blogs (pingbacks and trackbacks)” options (on the SETTINGS>DISCUSSION page) would perform the same functionality as unsetting the Pingback with the Filter you mentioned above? Or would it still actually get around this?
Now that’s a very good question. I’m interested in reading an answer to this too.
unchecking “Allow link notifications from other blogs” will certainly turn off pingbacks for future posts, though you would still need to go in and edit existing posts to disable it for them (bulk edit is your friend here). Filtering ‘xmlrpc_methods’ is just a much faster way to disable pingbacks site-wide.
The “Attempt to notify any blogs linked to from the article” controls whether you ping other sites that you’ve linked to in your posts. It still generates network traffic to those sites, but cannot be triggered remotely as this article is discussing. Leaving this enabled is fine.
ok, and if the site dont need pingbacks, would recommend the “add_filter(‘xmlrpc_enabled’,’__return_false’);” method?
if you don’t need XML-RPC at all, then sure. But it’s used for more than just pingback… notably Jetpack and any other service that you may have that posts to WordPress for you.
Yesterday I implemented Disable XML-RPC plugin in a couple sites and can confirm that at least JetPack stats are working. Also JetPack Post Views plugin works well too.
I don’t post items remotely so it looks like it’s safe to disable XML RPC in this particular type of cases.
Also, in websites where WP is used as a simple CMS, with no posts, just pages, it also should be safe to deactivate.
JetPack is still able to publish to Linkedin, Google+, Facebook and Twitter.
And services like dlvr.it are able to retrieve information to send to social networks.
Everything seems to work ok, yet the XML RPC is disabled as I can test it from http://xmlrpc.eritreo.it/
Hope this help others.
I know Will, but AFAIK, XML RPC is ONLY used when you publish from third parties TO WordPress, not in the opposite way. I deactivated XML RPC and didnt notice any malfunction in JetPack; I use Stats, Comments and Publish to social networks. What JetPack features would require XML RPC enabled? Post by Email? Monitor? JSON API?
Maybe I’m blind, but I don’t think XML RPC is a feature every site cannot live without. Please clarify if I’m wrong.
Thanks for the clarification Will 🙂
great article. very informative. thanks. the wp filters around ping backs, etc gives me the idea to create a plugin – that for example allows admin to determine blacklist & white list for ping-backers, track-backers, etc. might be neatly implemented as simple extension to existing wordpress firewall type plugins – eg: wp-anti-spammer-anti-splogger plugin. will look into it.
The plugin for disabling pingback functionality for your entire site:
https://wordpress.org/plugins/disable-pingbacks/
Some simple PHP lines in the beginning of the code on the attacked site might would have changed this whole story. Something like this maybe:
[code][/code]
I’ve tried using the suggested code snippet to disable trackbacks and I get the following:
PHP Notice: Use of undefined constant xe2x80x98xmlrpc_methodsxe2x80x99 – assumed ‘xe2x80x98xmlrpc_methodsxe2x80x99’ in /wp-content/themes/child-theme/functions.php on line 39, referer: /wp-admin/options-writing.php
I oringally want it to be a MU plugin, but gave the same error, so I moved it to be a normal plugin, same error and finally moved to the theme folder. I’m using WP 3.8.1 – wonder if anyone else has had the same problem, might know the answer?
Thanks for this. Unfortunately the code in your Update isn’t a complete solution: it contains erroneous “smartquotes,” it doesn’t work in PHP 5.2, and it’s not packaged as a plugin (although I guess an alternative would be to put it in a theme’s functions.php file, right?).
Has anybody put together a proper plugin, preferably compatible with PHP 5.2?
Try “Disable XML RPC” 😉 Worked for me under PHP 5.4 and 5.2 🙂
Sweet! Thanks. Link: https://wordpress.org/plugins/disable-xml-rpc/
The guts of the plugin is one line:
add_filter( ‘xmlrpc_enabled’, ‘__return_false’ );
I take it that will disable pingbacks, and possibly other applications of XML-RPC as well? Fine by me, just wanting to understand all the implications.
It blows my mind how sometimes something so simple can cause so much trouble. One little line of code in the wrong place at the wrong time can wreck havoc for thousands of people!
There’s a plugin here with the patch applied http://wpshed.com/wordpress-distributed-denial-service-attack-ddos-security-plugin/
Thanks so much for sharing this information, Daniel. I checked my site and breathed a sigh of relief. Cheers!
I’ve found one of my sites is being used in DDOS. I have installed “Disable XML-RPC Pingback” hopefully that’ll do the trick. I don’t use JetPack and I don’t think I’ll need the pingback.
How long were companies impacted (unable to access the internet) during this attack? How do these attacks affect productivity and corporate image? I have found a service from TW Telecom which sits at the peering points will remove packets during the attack but NOT interfere with the internet traffic flow so the company continues to function as if it were not happening…thoughts?
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Ok to sum it up will disabling “Allow link notifications from other blogs”, but leaving enabled “Attempt to notify any blogs linked to from the article” still present security risk to my site or do I need to disable both and maybe install a 3rd party plugin?
This is very interesting 🙂 Essentially with this you don’t even need zombies for DDOS, and its so easy to find WordPress websites these days, its almost all over the web.
maybe the site should do a dns check to see if the ip in of the pingback request matches the domain in the included url *before* doing a request to that url to check for links.(most likely it wouldn’t match in the case of such an attack if the attacker isn’t also doing some kind of dns hack (far less likely) or using the same same host (also far less likely) – stopping it right there
I think its a small thing that could make such misuse harder to do
also the way that caching is done obviously needs to be looked at too.
(as that in itself sounds like it presents a DOS risk for the site (not other sites though) – given the ram each process handling a php request needs on 64 bit platforms these days it wouldn’t need many concurrent requests to send most sites into hardcore swap if too many of them can’t be handled very quickly from cache.
Over the last 3 days, I have noticed a massive amount of traffic hitting my VPS client sites xmlrpc file. At one stage there were more than 100 bots per second. This flood successfully brought down two of our busy ecommerce sites, leading to client calls (clients don’t really know what a DDOS is and don’t care, they just want their site to work. Though they were patient, this kind of issue can cast a shadow on your service).
We tried a whole range of things to try to mitigate the issue, SYNFLOOD in our CSF firewall (no effect), Wordfence plugin (no effect), BRUTE protect plugin (no use).
Finally we blocked the file using
Order deny,allow Deny from allbut the bots simply turned to the theme index file and continued their DOS attack.Then we came up with a mod_sec rule which had more success:
SecRule REQUEST_LINE "POST .*wp-login.*" "pass,initcol:ip=%{REMOTE_ADDR},setvar:ip.maxlimit=+1,deprecatevar:ip.maxlimit=1/600,nolog,id:35011"
SecRule IP:MAXLIMIT "@gt 10" "log,deny,id:350111,msg:'wp-bruteforce: denying %{REMOTE_ADDR} (%{ip.maxlimit} connection attempts)'"
SecRule REQUEST_LINE "POST .*xmlrpc.*" "pass,initcol:ip=%{REMOTE_ADDR},setvar:ip.maxlimit=+1,deprecatevar:ip.maxlimit=1/600,nolog,id:35012"
SecRule IP:MAXLIMIT "@gt 2" "log,deny,id:350112,msg:'wp-bruteforce-xmlrpc: denying %{REMOTE_ADDR} (%{ip.maxlimit} connection attempts)'"
The problem with disabling xmlrpc is that a lot of plugins and sites use it legitimately. Removing it will break wordpress. I haven’t tried your suggested plugin / function, will give that a go.
Interesting approach, limiting the amount of connections by IP could work, but what about and attack with 500+ source IP. It could overflow the iptables list if your server has not enough RAM memory available.
Are those websites using some kind of cache? CDN? Using it may help to mitigate the cpu load and disk stress. But obviously, it must be correctly configured.
Yes, IP table list is limited to 500 entries, we also use cloudlinux to manage consecutive connections so that any one account cannot chew up the RAM.
We’ve also installed bruteprotect plugin and that is definitely helping.
We are now looking at cloudflare and cloudproxy and considering which to try. Cloudflare seems more comprehensive and cheaper than cloudproxy and I’m not sure why? What do you use?
Glad you asked. I do choose a variety of things: MySQL cache in the server + W3 Total Cache to generate html versions + CloudFlare to allocate those html versions + Amazon Cloudfront to allocate all the other files (images/js/css). This combination is a relief for Apache. Plugins: CSF in the server + WordFence + iThemes Security. All these elements provide a resilient configuration and almost 0% downtime. Obviously counting on a very reliable hosting service is the cornerstone for your online buildings.
If you need to solve the configuration with a professional approach don’t hesitate in contacting me.
All the best
Simply disabled xmlrpc and black listed ips logged with malicious requests
( verifying pingback from 195.154.136.19 ) I get attacked recently on and on from that source…
Use captcha on login form
This shows the importance of keeping up with your WordPress security. Thanks for the free scanner. I just checked and thankfully my site is clean.
is this still an issue w/newest WP? 4.3.1 as of today, i think.
Wow, this is spooky. I had no idea you could weaponize other people’s websites against another one.
Nice post Daniel, I basically delete the xmlrpc.php file from WordPress and it is the best way to get rid of these DDoS Attacks. This is useful method if you are not relying on Jetpack like plugins which uses xmlrpc file.
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