Defending Against DoS Attacks: Attacks

Our first post built a case for considering availability as an aspect of security context, rather than only confidentiality and integrity. This has been driven by Denial of Service (DoS) attacks, which are used by attackers in many different ways, including extortion (using the threat of an attack), obfuscation (to hide exfiltration), hacktivism (to draw attention to a particular cause), or even friendly fire (when a promotion goes a little too well). Understanding the adversary and their motivation is one part of the puzzle. Now let’s look at the types of DoS attacks you may face – attackers have many arrows in their quivers, and use them all depending on their objectives and targets. Flooding the Pipes The first kind of Denial of Service attack is really a blunt force object. It’s basically about trying to oversubscribe the bandwidth and computing resources of network (and increasingly server) devices to impact resource availability. These attacks aren’t very sophisticated, but as evidenced by the ongoing popularity of volume-based attacks, fairly effective effective. These tactics have been in use since before the Internet bubble, leveraging largely the same approach. But they have gotten easier with bots to do the heavy lifting. Of course, this kind of blasting must be done somewhat carefully to maintain the usefulness of the bot, so bot masters have developed sophisticated approaches to ensure their bots avoid ISPs penalty boxes. So you will see limited bursts of traffic from each bot and a bunch of IP address spoofing to make it harder to track down where the traffic is coming from, but even short bursts from 100,000+ bots can flood a pipe. Quite a few specific techniques have been developed for volumetric attacks, but most look like some kind of flood. In a network context, the attackers focus on overfilling the pipes. Floods target specific protocols (SYN, ICMP, UDP, etc.), and work by sending requests to a target using the chosen protocol, but not acknowledging the response. Enough of these outstanding requests limit the target’s ability to communicate. But attackers need to stay ahead of Moore’s Law, because targets’ ability to handle floods has improved with processing power. So network-based attacks may include encrypted traffic, forcing the target to devote additional computational resources to process massive amounts of SSL traffic. Given the resource-intensive nature of encryption, this type of attack can melt firewalls and even IPS devices unless they are configured specifically for large-scale SSL support. We also see some malformed protocol attacks, but these aren’t as effective nowadays, as even unsophisticated network security perimeter devices drop bad packets at wire speed. These volume-based attacks are climbing the stack as well, targeting web servers by actually completing connection requests and then making simple GET request and resetting the connection over and over again, with approximately the same impact as a volumetric attack – over-consumption of resources effectively knocking down servers. These attacks may also include a large payload to further consume bandwidth. The now famous Low Orbit Ion Cannon, a favorite tool of the hacktivist crowd, has undertaken a similar evolution, first targeting network resources and proceeding to now target web servers as well. It gets even better – these attacks can be magnified to increase their impact by simultaneously spoofing the target’s IP address and requesting sessions from thousands of other sites, which then bury the target in a deluge of misdirected replies, further consuming bandwidth and resources. Fortunately defending against these network-based tactics isn’t overly complicated, as we will discuss in the next post, but without a sufficiently large network device at the perimeter to block these attacks or an upstream service provider/traffic scrubber to dump offending traffic, devices fall over in short order. Overwhelming the Application But attackers don’t only attack the network – they increasingly attack the applications as well, following the rest of attackers up the stack. Your typical n-tier web application will have some termination point (usually a web server), an application server to handle application logic, and then a database to store the data. Attackers can target all tiers of the stack to impact application availability. So let’s dig into each layer to see how these attacks work. The termination point is usually the first target in application DoS attacks. They started with simple GET floods as described above, but quickly evolved to additional attack vectors. The best known application DoS attack is probably RSnake’s Slowloris, which consumes web server resources by sending partial HTTP requests, effectively opening connections and then leaving the sessions open by sending additional headers at regular intervals. This approach is far more efficient than the GET flood, requiring only hundreds of requests at regular intervals rather than constant thousands, and only requires one device to knock down a large site. These application attacks have evolved over time and now send complete HTTP requests to evade IDS and WAF devices looking for incomplete HTTP requests, but they tamper with payloads to confuse applications and consume resources. As defenders learn the attack vectors and deploy defenses, attackers evolve their attacks. The cycle continues. Web server based attacks can also target weaknesses in the web server platform. For example the Apache Killer attack sends a malformed HTTP range request to take advantage of an Apache vulnerability. The Apache folks quickly patched the code to address this issue, but it shows how attackers target weaknesses in the underlying application stack to knock the server over. And of course unpatched Apache servers are still vulnerable today at many organizations. Similarly, the RefRef attack leverages SQL injection to inject a rogue .js file onto a server, which then hammers a backend database into submission with seemingly legitimate traffic originating from an application server. Again, application and database server patches are available for the underlying infrastructure, but vulnerability remains if either patch is missing. Attackers can also target legitimate application functionality. One example of such an attack targets the search capability within a web site. If an attacker scripts a series of overly broad

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Incite 9/27/2012: They Own the Night

Our days just keep getting longer and longer. When the kids were younger afternoons and early evenings were a blur of activities, homework, hygiene, meals, reading, and then bed. Most nights the kids were in bed by 8:30 and the Boss and I could eat in peace, watch a little TV, catch up, and basically take a breath. But since XX1 entered middle school, things have changed. The kids have adapted fine. The Boss and me, not so much. Now it’s all about dividing and conquering. I handle the early shift and get the twins ready for school. They are on the bus by 7:20 and then I usually head over to some coffee shop and start working. The Boss handles XX1 and has her on the bus at 8:10, and then she starts her day of working through all the crap that has to happen to keep the trains running. The twins get off the bus at 3pm or so. Then it’s homework time and shuttling them off to activities. XX2 isn’t home until 4:30; then some days she can get an hour or two of work in, and other days she can’t. Inevitably she gets home from dance and has to start her homework. She usually wraps up around 10, but I usually get enlisted to help with the writing or math. And there are nights when XX1 is up until 11 or even later trying to get everything done. So there is no peace and quiet. Ever. We find ourselves staying up past midnight because those 90 minutes after all the kids go to bed are the only time we have to catch up and figure out the logistics for the next day. Which assumes that I don’t have work I need to get done. I know Rich has it harder right now with his 2 (and soon to be 3) kids under 4. I remember those days, and don’t miss the sleep deprivation. And I’m sure he misses sleeping in on weekends. At least I get to do that – our kids want us to sleep as late a possible, so they can watch more crappy shows on Nick Jr. But I do miss the quiet evenings after the kids were sleeping. Those are likely gone for a little while. For the next 9 years or so, the kids own the night. –Mike Photo credits: We Own The Night originally uploaded by KJGarbutt Heavy Research We’re back at work on a variety of blog series, so here is a list of the research currently underway. Remember you can get our Heavy Feed via RSS, where you can get all our content in its unabridged glory. And you can get all our research papers too. Defending Against Denial of Service (DoS) Attacks Introduction Securing Big Data Architectural Issues Security Issues with Hadoop Incite 4 U Responsible is in the eye of the beholder: My personal views on disclosure have changed a lot over the years. If you haven’t changed your views in the last 10 years you are either a hermit or a religious zealot – the operating environment has changed a lot. And the longer I have watched (and participated) in the debate, the more I realize it seems to be more about egos than the good of the public. And I fully mean this on all sides – researchers, vendors, users (but less), government, and pundits. Take Richard Bejtlich’s latest post on vendors or researchers going public when they find command and control servers. He expresses the legitimate concern that whoever finds and publicizes this information may often be blowing a law enforcement or intelligence operation. On the other hand law enforcement and intelligence agencies sure don’t make it easy to report these findings, and researchers might be sitting there watching people get compromised (including their customers). This is a hard problem to solve – if we even can. Just ask the Stratfor guys who were materially damaged while the FBI was not only watching, but ‘assisting’ the attack via their confidential informant. Better communication and cooperation is probably the answer, but I have absolutely no confidence that can happen at scale, even if some companies (including Richard’s employer) have those ties. No, I don’t have an answer, but we all need open minds, and probably a bit less ego and dogma. – RM The mark of a mature market: You can joke about the SC Magazine reviews operation. How they rarely actually test products, but instead sit through WebEx demos run by experienced SEs who make every product seem totally awesome. And that may be true but it’s not the point. It’s about relative ratings as an indicator of a mature market. If you look at SC Mag’s recent group test on email security devices, you’ll see 9 out of 10 products graded higher than 4 1/4 stars (out of 5). That 10th product must really suck for 3 stars. But even if you deflate the ratings by a star (or two) you’ll see very little outward differentiation. Which means the product category has achieved a lowest common denominator around a base set of features. So how do you decide between largely undifferentiated offerings? Price, of course… – MR Progress, at a glacial pace: I disagree with Mike Mimoso about the Disconnect Between Application Development and Security Getting Wider. We have been talking about this problem for almost a decade with not much improvement, so it certainly can feel that way. But I can say from personal experience that 10 years ago even the companies who developed security software knew nothing about secure code development, while now these is a better than even chance that someone on the team knows a little security. Have their processes changed to embrace security? Only at a handful of firms. The issue, in my opinion, is and has been the invisible boundary around the dev team to shield them from outside influence. Developers are largely isolated to keep

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Friday Summary: September 28, 2012 (A weird security week)

There was a lot of big news this week in the security world, most of it bad. Even if you skip the intro, make sure you read the Top News section. Rich here, Growing up I was – and this might shock some of you – a bit of a nerd. I glommed onto computers and technology pretty much as soon as I had access to them, and when I didn’t I was reading books and watching shows that painted wonderful visions of the future. I was a hacker before I ever heard the word, constantly taking things apart to see how they worked, then building my own versions. Technology is thus very intuitive to me. I never had to learn it in the same way as people coming to computers and electronics later in life. I began programming so early in life that it keyed into the same (maybe) brain pathways that allow children to learn multiple languages with far more facility than adults. While my generational peers are far more comfortable with technology and computers than our parents, I generally still have a leg up due to my early immersion. I naturally assumed that the generations following me would grow up closer to my experiences than my less geeky peers. But much to my surprise, although they are very comfortable with computers, they don’t have the damnedest idea of how they work or how to bend them to their own will. Unless it involves cats and PowerPoint. Lacking teachers who understood tech, they grow up learning how to use Office, not to program or dig into technology beyond the shallowest surface levels. As I have started raising my own kids, I worry about how to get them interested in technology, and algorithmic thinking, in a world where iPads put the entire Disney repository a few taps away. I’m not talking about forcing them to become programmers, but taking advantage of their brain plasticity to reinforce logical thinking and problem solving, and at least convey a sense of deeper exploration. This really did worry me, but over the past few months I have realized that as a parent I have the opportunity to engage my children to degrees my parents couldn’t possibly imagine. It was a big deal when I got my first Radio Shack electronics kit. It was even a bigger deal when I made my first radio. My kids? This past weekend my 3.5 and 2 year old got to play with their first home-built LEGO robot. Yes, I did most of the building and all the programming, but I could see them learning the foundation of how it worked and what we could make it do. Building a robot to play with our cat is a hell of a lot more exciting than putting a picture of a cat in a PowerPoint. This is barely the start. I grew up pushing ASCII pixels on screens. They will grow up programming, and perhaps designing, autonomous flying drones with high-definition video feeds. I grew up making simple electric candles that would turn on in a dark room. They will be able to create wonderful microcontroller-based objects they then embed into 3-D printed housings. There’s no guarantee they will actually be interested in these things, but social engineering isn’t just for pen testing. Hopefully I can manipulate the crap out of them so they at least get the basics. And, if not, it means more stock fab material for me. I’m biased. I think most of my success in life is due to a combination of logical thinking, the exploratory drive of a hacker, and a modest facility with the written word. As a parent I now have tools to teach these skills to my children in ways our parents could only dream about. On to the Summary: Webcasts, Podcasts, Outside Writing, and Conferences Rich quoted on the myth of cyberinsurance. Mike’s Security Intelligence post at Dark Reading. Favorite Securosis Posts Adrian Lane: My Security Fail (and Recovery) for the Week. Gave me a moment of panic. Mike Rothman: Securing Big Data: Architectural Issues. This series is critical for you to learn what’s coming. If it hasn’t already arrived. Rich: David Mortman’s Another Inflection Point. The more we let go of, the more we can do. Other Securosis Posts Defending Against DoS Attacks: The Attacks. Incite 9/27/2012: They Own the Night. New Research Paper: Pragmatic WAF Management. Favorite Outside Posts Adrian Lane: OAuth 2.0 – Google Learns to Crawl. For someone learning just how much I don’t know about authorization, this is a good overview of the high points of the OAuth security discussion. Mike Rothman: 25 Great Quotes from the Princess Bride. 25 YEARS! WTF? I don’t feel that old, but I guess I am. Take a trip down memory lane and remember one of the better movies ever filmed. IMHO, anyway. Rich: Connect with your inner grey hat. The title is a bit misleading, but the content is well stated. You need to change up your thinking constantly. Research Reports and Presentations Pragmatic WAF Management: Giving Web Apps a Fighting Chance. Understanding and Selecting Data Masking Solutions. Evolving Endpoint Malware Detection: Dealing with Advanced and Targeted Attacks. Implementing and Managing a Data Loss Prevention Solution. Defending Data on iOS. Malware Analysis Quant Report. Report: Understanding and Selecting a Database Security Platform. Top News and Posts The big news this week is the compromise and use of an Adobe code signing certificate in targeted attacks. Very serious indeed. Banks still fighting off the Iranian DDoS attacks. OpenBTS on Android. This is the software you use to fake a cell phone base tower. Smart grid control vendor hacked. Yes, they had deep access to their clients, why do you ask? An interview with the author of XKCD. Sudo read this article. PHPMyadmin backdoored. PPTP now really and truly dead. More Java 0day. Seriously, what the hell is going on this week? And to top everything off, a Sophos post

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