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Security and Privacy in Cloud Computing

Security and Privacy in Cloud Computing. Ragib Hasan Johns Hopkins University en.600.412 Spring 2011. Lecture 11 04/25/2011. Attacking Availability. Goal: To see how availability of a cloud can be affected by DoS attacks launched from inside the cloud. Review Assignment #10:

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Security and Privacy in Cloud Computing

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  1. Security and Privacy in Cloud Computing Ragib HasanJohns Hopkins Universityen.600.412 Spring 2011 Lecture 11 04/25/2011

  2. Attacking Availability • Goal: To see how availability of a cloud can be affected by DoS attacks launched from inside the cloud. • Review Assignment #10: • Han Liu, A New Form of DOS Attack in a Cloud and Its Avoidance Mechanism, ACM Cloud Computing Security Workshop 2010 en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  3. Announcement • Next week (5/2), we’ll have our final class, where we will discuss • A wrap-up of things we learned • A high level view of cloud security problem space • No new papers will be discussed next week (but you do have to turn in Review Assignment #10 by 5/2) en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  4. Recap: Anti-virus as a service Pros Cons Ideas en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  5. DoS attack on cloud • Network provisioning in data centers: • Many servers share the same link/router, so bandwidth is shared. en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  6. Data center networks are typically grossly under-provisioned • Typical ratios are 2.5:1 to 8:1 • 8:1 means servers get at most 1/8 of the bandwidth of their interface • Bandwidth is limited by the hierarchical nature of network, routers, and switches • Multiplexing in routers reduce the amount of bandwidth each server ultimately gets en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  7. Typical data center network Communication between H1-H4 and H5-H8 are routed through R5 and R6. en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  8. Under provisioning is not a problem in traditional networks Network admins can co-locate related servers in the same subnet Network admins can redesign network topologies to fine tune for worst case performance en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  9. Under provisioning IS a problem in clouds There are many more servers in a cloud, so provisioning ratios are much higher (e.g. 45:1) Many clients use the same network, and malicious clients can launch DoS Application owner/designer has no control over network topology en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  10. DoS attacks on clouds DoS attacks on traditional systems (from the outside) can be prevented via clever tricks such as moving to a cloud based virtualized model DoS attacks on clouds launched from *inside* the cloud are much harder to prevent en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  11. DoS attack on clouds Adversary launches attack from inside the cloud data center network After probing the network and reverse-engineering the topology, the adversary can identify bottlenecks Then the adversary can send DoS traffic to the bottleneck link to saturate it en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  12. Example To attack Link B, adversary sends packets from R1’s subnet to another subnet en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  13. Types of attacks Untargeted attack: No particular link or host is targeted Targeted attack: Adversary gains critical mass in a network to target a specific victim en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  14. Topology identification Knowledge of topology is important for the adversary en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  15. How to identify topology • Technique #1: Traceroute • Run traceroute between all pairs of hosts • Due to ip provisioning schemes, running traceroute for a few pairs of hosts is enough • Disadvantages: • Can’t identify switches (layer 2) • Can be disabled at router level en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  16. How to identify topology • Technique #2: Network probing • Idea: Use observed traffic rates to infer number of router between two hosts en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  17. How many malicious hosts is enough? • Untargeted attack: • Easy to get many hosts if VM assignment algorithm can be reverse engineered (as in “Hey You!” paper • Even brute force attack succeeds in getting many hosts in the same subnet • (Note: this is different fro co-location attack, where the goal was to co-locate of physical hardware rather than network) en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  18. How many malicious hosts is enough? • Targeted attack: • Pick victim, launch brute force attacks • Tests show it is easy to get VMs in same subnet as target en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  19. Launching the attack • Process: • Send a flood of packets through the link • UDP used. (Why?) • For adaptive applications, do not saturate link completely, rather “almost” saturate it (Why?) en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  20. Mitigation strategy Use a user side monitoring agent to monitor link saturation When a link degrades, or server detects bottleneck and sends help packet, the monitor initiates app migration en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

  21. Comments Experiments / attacks were run on a real cloud (without knowledge of data center admin) en.600.412 Spring 2011 Lecture 11 | JHU | Ragib Hasan

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