|By Lori MacVittie||
|May 1, 2014 09:00 AM EDT||
This week's "bad news" with respect to information security centers on Facebook and the exploitation of HTTP caches to affect a DDoS attack. Reported as a 'vulnerability', this exploit takes advantage of the way the application protocol is designed to work. In fact, the same author who reports the Facebook 'vulnerability' has also shown you can use Google to do the same thing. Just about any site that enables you to submit content containing links and then retrieves those links for you (for caching purposes) could be used in this way. It's not unique to Facebook or Google, for that matter, they just have the perfect environment to make such an exploit highly effective.
The exploit works by using a site (in this case Facebook) to load content and takes advantage of the general principle of amplification to effectively DDoS a third-party site. This is a flood-based like attack, meaning it's attempting to overwhelm a server by flooding it with requests that voraciously consume server-side resources and slow everyone down - to the point of forcing it to appear "down" to legitimate users.
The requests brokered by Facebook are themselves 110% legitimate requests. The requests for an image (or PDF or large video file) are well-formed, and nothing about the requests on an individual basis could be detected as being an attack. This is, in part, why the exploit works: because the individual requests are wholly legitimate requests.
How it Works
The trigger for the "attack" is the caching service. Caches are generally excellent at, well, caching static objects with well-defined URIs. A cache doesn't have a problem finding /myimage.png. It's either there, or it's not and the cache has to go to origin to retrieve it. Where things get more difficult is when requests for content are dynamic; that is, they send parameters that the origin server interprets to determine which image to send, e.g. /myimage?id=30. This is much like an old developer trick to force the reload of dynamic content when browser or server caches indicate a match on the URL. By tacking on a random query parameter, you can "trick" the browser and the server into believing it's a brand new object, and it will go to origin to retrieve it - even though the query parameter is never used. That's where the exploit comes in.
HTTP servers accept as part of the definition of a URI any number of variable query parameters. Those parameters can be ignored or used at the discretion of the application. But when the HTTP server is looking to see if that content has been served already, it does look at those parameters. The reference for a given object is its URL, and thus tacking on a query parameter forces (or tricks if you prefer) the HTTP server to believe the object has never been served before and thus can't be retrieved from a cache.
Caches act on the same principles as an HTTP server because when you get down to brass tacks, a cache is a very specialized HTTP server, focused on mirroring content so it's closer to the user.
<img src=http://target.com/file?r=1> <img src=http://target.com/file?r=2> <img src=http://target.com/file?r=3> ... <img src=http://target.com/file?r=1000>
Many, many, many, many (repeat as necessary) web applications are built using such models. Whether to retrieve text-based content or images is irrelevant to the cache. The cache looks at the request and, if it can't match it somehow, it's going to go to origin.
Which is what's possible with Facebook Notes and Google. By taking advantage of (exploiting) this design principle, if a note crafted with multiple image objects retrieved via a dynamic query is viewed by enough users at the same time, the origin can become overwhelmed or its network oversubscribed.
This is what makes it an exploit, not a vulnerability. There's nothing wrong with the behavior of these caches - they are working exactly as they were designed to act with respect to HTTP. The problem is that when the protocol and caching behavior was defined, such abusive behavior was not considered.
In other words, this is a protocol exploit not specific to Facebook (or Google). In fact, similar exploits have been used to launch attacks in the past. For example, consider some noise raised around WordPress in March 2014 that indicated it was being used to attack other sites by bypassing the cache and forcing a full reload from the origin server:
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.
The WordPress exploit was taking advantage of the way "pingbacks" work. Attackers were using sites to add pingbacks to amplify an attack on a third party site (also, ironically, a WordPress site).
It's not just Facebook, or Google - it's inherent in the way caching is designed to work.
Not Just HTTP
This isn't just an issue with HTTP. We can see similar behavior in a DNS exploit that renders DNS caching ineffective as protection against certain attack types. In the DNS case, querying a cache with a random host name results in a query to the authoritative (origin) DNS service. If you send enough random host names at the cache, eventually the DNS service is going to feel the impact and possibly choke.
In general, these types of exploits are based on protocol and well-defined system behavior. A cache is, by design, required to either return a matching object if found or go to the origin server if it is not. In both the HTTP and DNS case, the caching services are acting properly and as one would expect.
The problem is that this proper behavior can be exploited to affect a DDoS attack - against third-parties in the case of Facebook/Google and against the domain owner in the case of DNS.
These are not vulnerabilities, they are protocol exploits. This same "vulnerability" is probably present in most architectures that include caching. The difference is that Facebook's ginormous base of users allows for what is expected behavior to quickly turn into what looks like an attack.
The general consensus right now is the best way to mitigate this potential "attack" is to identify and either rate limit or disallow requests coming from Facebook's crawlers by IP address. In essence, the suggestion is to blacklist Facebook (and perhaps Google) to keep it from potentially overwhelming your site.
The author noted in his post regarding this exploit that:
Facebook crawler shows itself as facebookexternalhit. Right now it seems there is no other choice than to block it in order to avoid this nuisance.
The post was later updated to note that blocking by agent may not be enough, hence the consensus on IP-based blacklisting.
The problem is that attackers could simply find another site with a large user base (there are quite a few of them out there with the users to support a successful attack) and find the right mix of queries to bypass the cache (cause caches are a pretty standard part of a web-scale infrastructure) and voila! Instant attack.
Blocking Facebook isn't going to stop other potential attacks and it might seriously impede revenue generating strategies that rely on Facebook as a channel. Rate limiting based on inbound query volume for specific content will help mitigate the impact (and ensure legitimate requests continue to be served) but this requires some service to intermediate and monitor inbound requests and, upon seeing behavior indicative of a potential attack, the ability to intercede or apply the appropriate rate limiting policy. Such a policy could go further and blacklist IP addresses showing sudden increases in requests or simply blocking requests for the specified URI in question - returning instead some other content.
Another option would be to use a caching solution capable of managing dynamic content. For example, F5 Dynamic Caching includes the ability to designate parameters as either indicative of new content or not. That is, the caching service can be configured to ignore some (or all) parameters and serve content out of cache instead of hammering on the origin server.
Let's say the URI for an image was: /directory/images/dog.gif?ver=1;sz=728X90 where valid query parameters are "ver" (version) and "sz" (size). A policy can be configured to recognize "ver" as indicative of different content while all other query parameters indicate the same content and can be served out of cache. With this kind of policy an attacker could send any combination of the following and the same image would be served from cache, even though "sz" is different and there are random additional query parameters.
/directory/images/dog.gif?ver=1;sz=728X90; id=1234 /directory/images/dog.gif?ver=1;sz=728X900; id=123456 /directory/images/dog.gif?ver=1;sz=728X90; cid=1234
By placing an application fluent cache service in front of your origin servers, when Facebook (or Google) comes knocking, you're able to handle the load.
There have been no reports of an attack stemming from this exploitable condition in Facebook Notes or Google, so blacklisting crawlers from either Facebook or Google seems premature. Given that this condition is based on protocol behavior and system design and not a vulnerability unique to Facebook (or Google), though, it would be a good idea to have a plan in place to address, should such an attack actually occur - from there or some other site.
You should review your own architecture and evaluate its ability to withstand a sudden influx of dynamic requests for content like this, and put into place an operational plan for dealing with it should such an event occur.
For more information on protecting against all types of DDoS attacks, check out a new infographic we’ve put together here.
SYS-CON Events announced today that Vicom Computer Services, Inc., a provider of technology and service solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. They are located at booth #427. Vicom Computer Services, Inc. is a progressive leader in the technology industry for over 30 years. Headquartered in the NY Metropolitan area. Vicom provides products and services based on today’s requirements around Unified Networks, Cloud Computing strategies, Virtualization around Software defined Data Ce...
Apr. 18, 2015 02:00 PM EDT Reads: 1,349
SYS-CON Events announced today that Tufin, the market-leading provider of Security Policy Orchestration Solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. As the market leader of Security Policy Orchestration, Tufin automates and accelerates network configuration changes while maintaining security and compliance. Tufin's award-winning Orchestration Suite™ gives IT organizations the power and agility to enforce security policy across complex, multi-vendor enterprise networks. With more than 1...
Apr. 18, 2015 01:45 PM EDT Reads: 3,246
SYS-CON Events announced today that Optimal Design, an Internet of Things solution provider, will exhibit at SYS-CON's Internet of @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Optimal Design is an award winning product development firm offering industrial design and engineering services to the consumer, medical, and defense markets.
Apr. 18, 2015 01:45 PM EDT Reads: 1,579
SYS-CON Events announced today that MangoApps will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY., and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. MangoApps provides private all-in-one social intranets allowing workers to securely collaborate from anywhere in the world and from any device. Social, mobile, and easy to use. MangoApps has been named a "Market Leader" by Ovum Research and a "Cool Vendor" by Gartner...
Apr. 18, 2015 01:15 PM EDT Reads: 3,533
SYS-CON Events announced today that Cloudian, Inc., the leading provider of hybrid cloud storage solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cloudian, Inc., is a Foster City, California - based software company specializing in cloud storage software. The main product is Cloudian, an Amazon S3-compliant cloud object storage platform, the bedrock of cloud computing systems, that enables cloud service providers and enterprises to build reliable, affordable and scalable cloud storage solu...
Apr. 18, 2015 01:00 PM EDT Reads: 2,317
SYS-CON Events announced today that Gridstore™, the leader in hyper-converged infrastructure purpose-built to optimize Microsoft workloads, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Gridstore™ is the leader in hyper-converged infrastructure purpose-built for Microsoft workloads and designed to accelerate applications in virtualized environments. Gridstore’s hyper-converged infrastructure is the industry’s first all flash version of HyperConverged Appliances that include both compute and storag...
Apr. 18, 2015 12:45 PM EDT Reads: 4,180
SYS-CON Events announced today that Creative Business Solutions will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Creative Business Solutions is the top stocking authorized HP Renew Distributor in the U.S. Based out of Long Island, NY, Creative Business Solutions offers a one-stop shop for a diverse range of products including Proliant, Blade and Industry Standard Servers, Networking, Server Options and Care Packs. As a trusted supplier, CBS guarantees quality controlled stock levels thanks to an Auto...
Apr. 18, 2015 12:30 PM EDT Reads: 4,233
How is unified communications transforming the way businesses operate? In his session at WebRTC Summit, Arvind Rangarajan, Director of Product Marketing at BroadSoft, will discuss how to extend unified communications experience outside the enterprise through WebRTC. He will also review use cases across different industry verticals. Arvind Rangarajan is Director, Product Marketing at BroadSoft. He has over 19 years of experience in the telecommunications industry in various roles such as Software Development, Product Management and Product Marketing, applied across Wireless, Unified Communic...
Apr. 18, 2015 12:30 PM EDT Reads: 1,570
The 17th International Cloud Expo has announced that its Call for Papers is open. 17th International Cloud Expo, to be held November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, APM, APIs, Microservices, Security, Big Data, Internet of Things, DevOps and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportunity. Submit your speaking proposal today!
Apr. 18, 2015 12:00 PM EDT Reads: 2,051
SYS-CON Events announced today that IDenticard will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. IDenticard™ is the security division of Brady Corp (NYSE: BRC), a $1.5 billion manufacturer of identification products. We have small-company values with the strength and stability of a major corporation. IDenticard offers local sales, support and service to our customers across the United States and Canada. Our partner network encompasses some 300 of the world's leading systems integrators and security s...
Apr. 18, 2015 12:00 PM EDT Reads: 4,878
What exactly is a cognitive application? In her session at 16th Cloud Expo, Ashley Hathaway, Product Manager at IBM Watson, will look at the services being offered by the IBM Watson Developer Cloud and what that means for developers and Big Data. She'll explore how IBM Watson and its partnerships will continue to grow and help define what it means to be a cognitive service, as well as take a look at the offerings on Bluemix. She will also check out how Watson and the Alchemy API team up to offer disruptive APIs to developers.
Apr. 18, 2015 12:00 PM EDT Reads: 1,422
The IoT Bootcamp is coming to Cloud Expo | @ThingsExpo on June 9-10 at the Javits Center in New York. Instructor. Registration is now available at http://iotbootcamp.sys-con.com/ Instructor Janakiram MSV previously taught the famously successful Multi-Cloud Bootcamp at Cloud Expo | @ThingsExpo in November in Santa Clara. Now he is expanding the focus to Janakiram is the founder and CTO of Get Cloud Ready Consulting, a niche Cloud Migration and Cloud Operations firm that recently got acquired by Aditi Technologies. He is a Microsoft Regional Director for Hyderabad, India, and one of the f...
Apr. 18, 2015 12:00 PM EDT Reads: 934
With IoT exploding, massive data will transform businesses with opportunities to monetize almost anything that can be measured. In this C-Level Roundtable Discussion at @ThingsExpo, Brendan O’Brien, Aria Systems Co-founder and Chief Evangelist, will lead an expert panel of consultants, thought leaders and practitioners who will look at these new monetization trends, discuss the implications, and detail lessons learned from their collective experience. Finally, the panel will point the way forward for enterprises who wish to leverage the resulting complex recurring revenue models, adding valu...
Apr. 18, 2015 11:00 AM EDT Reads: 1,409
SYS-CON Events announced today that Ciqada will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Ciqada™ makes it easy to connect your products to the Internet. By integrating key components - hardware, servers, dashboards, and mobile apps - into an easy-to-use, configurable system, your products can quickly and securely join the internet of things. With remote monitoring, control, and alert messaging capability, you will meet your customers' needs of tomorrow - today! Ciqada. Let your products take flight. For more inform...
Apr. 18, 2015 07:00 AM EDT Reads: 1,567
SYS-CON Events announced today that GENBAND, a leading developer of real time communications software solutions, has been named “Silver Sponsor” of SYS-CON's WebRTC Summit, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. The GENBAND team will be on hand to demonstrate their newest product, Kandy. Kandy is a communications Platform-as-a-Service (PaaS) that enables companies to seamlessly integrate more human communications into their Web and mobile applications - creating more engaging experiences for their customers and boosting collaboration and productiv...
Apr. 18, 2015 06:00 AM EDT Reads: 2,241
SYS-CON Events announced today that BroadSoft, the leading global provider of Unified Communications and Collaboration (UCC) services to operators worldwide, has been named “Gold Sponsor” of SYS-CON's WebRTC Summit, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. BroadSoft is the leading provider of software and services that enable mobile, fixed-line and cable service providers to offer Unified Communications over their Internet Protocol networks. The Company’s core communications platform enables the delivery of a range of enterprise and consumer calling...
Apr. 18, 2015 05:30 AM EDT Reads: 2,169
VoxImplant has announced full WebRTC support in the newest versions of its Android SDK and iOS SDK. The updated SDKs, which enable audio and video calls on mobile devices, are now compatible with the WebRTC standard to allow any mobile app to communicate with WebRTC-enabled browsers, including Google Chrome, Mozilla Firefox, Opera, and, when available, Microsoft Spartan. The WebRTC-updated SDKs represent VoxImplant's continued leadership in simplifying the development of real-time communications (RTC) services for app developers. VoxImplant (built by Zingaya, the real-time communication servi...
Apr. 18, 2015 02:45 AM EDT Reads: 1,794
SYS-CON Events announced today that AIC, a leading provider of OEM/ODM server and storage solutions, will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. AIC is a leading provider of both standard OTS, off-the-shelf, and OEM/ODM server and storage solutions. With expert in-house design capabilities, validation, manufacturing and production, AIC's broad selection of products are highly flexible and are configurable to any form factor or custom configuration. AIC leads the industry with nearly 20 years of ...
Apr. 18, 2015 12:15 AM EDT Reads: 4,663
Buzzword alert: Microservices and IoT at a DevOps conference? What could possibly go wrong? Join this panel of experts as they peel away the buzz and discuss the important architectural principles behind implementing IoT solutions for the enterprise. As remote IoT devices and sensors become increasingly intelligent, they become part of our distributed cloud environment, and we must architect and code accordingly. At the very least, you’ll have no problem filling in your buzzword bingo cards.
Apr. 16, 2015 05:30 PM EDT Reads: 2,101
Internet of Things (IoT) will be a hybrid ecosystem of diverse devices and sensors collaborating with operational and enterprise systems to create the next big application. In their session at @ThingsExpo, Bramh Gupta, founder and CEO of robomq.io, and Fred Yatzeck, principal architect leading product development at robomq.io, will discuss how choosing the right middleware and integration strategy from the get-go will enable IoT solution developers to adapt and grow with the industry, while at the same time reduce Time to Market (TTM) by using plug and play capabilities offered by a robust I...
Apr. 13, 2015 12:15 PM EDT Reads: 1,875