|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 ElasticBox is holding a Hackathon at DevOps Summit, November 6 from 12 pm -4 pm at the Santa Clara Convention Center in Santa Clara, CA. You can enter as an individual or team of up to 10 developers. A New Star Is Born Every Month! All completed ElasticBoxes will then be sent to a judging panel - 12 winners will be featured on the ElasticBox website in 2015. All entrants will receive five full enterprise licenses for one year + ElasticBox headphones + Elasti...
Oct. 22, 2014 08:30 AM EDT Reads: 1,188
Once the decision has been made to move part or all of a workload to the cloud, a methodology for selecting that workload needs to be established. How do you move to the cloud? What does the discovery, assessment and planning look like? What workloads make sense? Which cloud model makes sense for each workload? What are the considerations for how to select the right cloud model? And how does that fit in with the overall IT tranformation? In his session at 15th Cloud Expo, John Hatem, head of V...
Oct. 22, 2014 08:00 AM EDT Reads: 1,206
Cloud services are the newest tool in the arsenal of IT products in the market today. These cloud services integrate process and tools. In order to use these products effectively, organizations must have a good understanding of themselves and their business requirements. In his session at 15th Cloud Expo, Brian Lewis, Principal Architect at Verizon Cloud, will outline key areas of organizational focus, and how to formalize an actionable plan when migrating applications and internal services to...
Oct. 22, 2014 07:45 AM EDT Reads: 1,154
SAP is delivering break-through innovation combined with fantastic user experience powered by the market-leading in-memory technology, SAP HANA. In his General Session at 15th Cloud Expo, Thorsten Leiduck, VP ISVs & Digital Commerce, SAP, will discuss how SAP and partners provide cloud and hybrid cloud solutions as well as real-time Big Data offerings that help companies of all sizes and industries run better. SAP launched an application challenge to award the most innovative SAP HANA and SAP ...
Oct. 22, 2014 07:00 AM EDT Reads: 1,337
Ixia develops amazing products so its customers can connect the world. Ixia helps its customers provide an always-on user experience through fast, secure delivery of dynamic connected technologies and services. Through actionable insights that accelerate and secure application and service delivery, Ixia's customers benefit from faster time to market, optimized application performance and higher-quality deployments.
Oct. 21, 2014 09:00 PM EDT Reads: 1,346
SYS-CON Events announced today that Calm.io has been named “Bronze Sponsor” of DevOps Summit Silicon Valley, which will take place on November 4–6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Calm.io is a cloud orchestration platform for AWS, vCenter, OpenStack, or bare metal, that runs your CL tools puppet, Chef, shell, git, Jenkins, nagios, and will soon support New Relic and Docker. It can run hosted, or on premise and provides VM automation / expiry, self-service portals,...
Oct. 21, 2014 08:45 PM EDT Reads: 1,228
In her General Session at 15th Cloud Expo, Anne Plese, Senior Consultant, Cloud Product Marketing, at Verizon Enterprise, will focus on finding the right mix of renting vs. buying Oracle capacity to scale to meet business demands, and offer validated Oracle database TCO models for Oracle development and testing environments. Anne Plese is a marketing and technology enthusiast/realist with over 19+ years in high tech. At Verizon Enterprise, she focuses on driving growth for the Verizon Cloud pla...
Oct. 21, 2014 07:30 PM EDT Reads: 1,301
SYS-CON Events announced today that Aria Systems, the recurring revenue expert, has been named "Bronze Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Aria Systems helps leading businesses connect their customers with the products and services they love. Industry leaders like Pitney Bowes, Experian, AAA NCNU, VMware, HootSuite and many others choose Aria to power their recurring revenue bu...
Oct. 21, 2014 06:00 PM EDT Reads: 1,213
The Internet of Things (IoT) is going to require a new way of thinking and of developing software for speed, security and innovation. This requires IT leaders to balance business as usual while anticipating for the next market and technology trends. Cloud provides the right IT asset portfolio to help today’s IT leaders manage the old and prepare for the new. Today the cloud conversation is evolving from private and public to hybrid. This session will provide use cases and insights to reinforce t...
Oct. 21, 2014 05:15 PM EDT Reads: 1,203
As Platform as a Service (PaaS) matures as a category, developers should have the ability to use the programming language of their choice to build applications and have access to a wide array of services. Bluemix is IBM's open cloud development platform that enables users to easily build cloud-based, creative mobile and web applications without having to spend large amounts of time and resources on configuring infrastructure and multiple software licenses. In this track, you will learn about the...
Oct. 21, 2014 05:00 PM EDT Reads: 1,250
Blue Box has closed a $10 million Series B financing. The round was led by a strategic investor and included participation from prior investors including Voyager Capital and Founders Collective, as well as the Blue Box executive team. This round follows a $4.3 million Series A closed in December of 2012 and led by Voyager Capital. In May of this year, the company announced general availability of its private cloud as a service offering, Blue Box Cloud. Since that release, the company has dem...
Oct. 21, 2014 01:45 PM EDT Reads: 1,491
SYS-CON Events announced today that Verizon has been named "Gold Sponsor" of SYS-CON's 15th International Cloud Expo®, which will take place on November 4-6, 2014, at the Santa Clara Convention Center in Santa Clara, CA. Verizon Enterprise Solutions creates global connections that generate growth, drive business innovation and move society forward. With industry-specific solutions and a full range of global wholesale offerings provided over the company's secure mobility, cloud, strategic network...
Oct. 21, 2014 09:30 AM EDT Reads: 1,536
SimpleECM is the only platform to offer a powerful combination of enterprise content management (ECM) services, capture solutions, and third-party business services providing simplified integrations and workflow development for solution providers. SimpleECM is opening the market to businesses of all sizes by reinventing the delivery of ECM services. Our APIs make the development of ECM services simple with the use of familiar technologies for a frictionless integration directly into web applicat...
Oct. 20, 2014 10:00 PM EDT Reads: 1,652
The only place to be June 9-11 is Cloud Expo & @ThingsExpo 2015 East at the Javits Center in New York City. Join us there as delegates from all over the world come to listen to and engage with speakers & sponsors from the leading Cloud Computing, IoT & Big Data companies. Cloud Expo & @ThingsExpo are the leading events covering the booming market of Cloud Computing, IoT & Big Data for the enterprise. Speakers from all over the world will be hand-picked for their ability to explore the economic...
Oct. 20, 2014 07:00 PM EDT Reads: 1,972
Cloudwick, the leading big data DevOps service and solution provider to the Fortune 1000, announced Big Loop, its multi-vendor operations platform. Cloudwick Big Loop creates greater collaboration between Fortune 1000 IT staff, developers and their database management systems as well as big data vendors. This allows customers to comprehensively manage and oversee their entire infrastructure, which leads to more successful production cluster operations, and scale-out. Cloudwick Big Loop supports ...
Oct. 20, 2014 05:45 PM EDT Reads: 1,672
To manage complex web services with lots of calls to the cloud, many businesses have invested in Application Performance Management (APM) and Network Performance Management (NPM) tools. Together APM and NPM tools are essential aids in improving a business’s infrastructure required to support an effective web experience… but they are missing a critical component – Internet visibility. Internet connectivity has always played a role in customer access to web presence, but in the past few years use...
Oct. 20, 2014 05:00 PM EDT Reads: 1,685
Oct. 20, 2014 05:00 PM EDT Reads: 1,901
Software AG helps organizations transform into Digital Enterprises, so they can differentiate from competitors and better engage customers, partners and employees. Using the Software AG Suite, companies can close the gap between business and IT to create digital systems of differentiation that drive front-line agility. We offer four on-ramps to the Digital Enterprise: alignment through collaborative process analysis; transformation through portfolio management; agility through process automation...
Oct. 20, 2014 03:45 PM EDT Reads: 1,691
Headquartered in Santa Monica, California, Bitium was founded by Kriz and Erik Gustavson. The 1,500 cloud-based application using Bitium’s analytics, app management, and single sign-on services include bug trackers, customer service dashboards, Google Apps, and social networks. The firm states website administrators can do multiple tasks online without revealing passwords. Bitium’s advisors include Microsoft’s former CMO and the former senior vice president of strategy, the founder and CEO of Li...
Oct. 20, 2014 03:00 PM EDT Reads: 1,784
What are the benefits of using an enterprise-grade orchestration platform? In their session at 15th Cloud Expo, Jeff Tegethoff, CEO of Appcore, and Kedar Poduri, Senior Director of Product Management at Citrix Systems, will take a closer look at the architectural design factors needed to support diverse workloads and how to run these workloads efficiently as a service provider. They will also discuss how to deploy private cloud environments in 15 minutes or less.
Oct. 20, 2014 03:00 PM EDT Reads: 1,699