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Stressing and Stretching

Stressing and Stretching. John A Clark with acknowledgements to Peter Laurens, Simon Poulding, Chetan Padia, Rob Alexander and Mark Harman. Smarter Stress. Server. The Usual Denial of Service Attack. Smarter DoS: Low Rate Attack. Server.

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Stressing and Stretching

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  1. Stressing and Stretching John A Clark with acknowledgements to Peter Laurens, Simon Poulding, Chetan Padia, Rob Alexander and Mark Harman

  2. Smarter Stress Server The Usual Denial of Service Attack

  3. Smarter DoS: Low Rate Attack Server Need only fill up buffer and then feed the server as it dispatches

  4. Smarter DoS: Low Rate Attack Server Need only fill up buffer and then feed the server as it dispatches

  5. Goal • Example basically shows that you can cause a lot of stress with little effort. • Usually just want to find test data inputs to stress system. • Question: can we devise a smart stressing language in which we can evolve interaction strategies. • Can the low rate DoS attack be discovered? • Have some preliminary results for stressing a system based on notion of music: notes/bars emphasis etc.

  6. Other Input Strategy • Perhaps one of the simplest “strategies” for choice of successive inputs is to specify a distribution. • For Boolean inputs – perhaps biased coin tossing • But more subtle input vectors can be created if we get rid of the usual independence assumption and embrace correlation of inputs. • Can evolve distributions to target specified achievement goals. • Motivated initially by Thevenod-Fosse et al work on “statistical testing” • Maximise the probability of the least covered element being covered. • Biut could test with an “inverted coverage criterion” – so that risky but little used or difficult to reach parts of the system state can be covered more. • In short, possibilities of evolving an input distribution for achieving some specified effect.

  7. Warping Systems 1 • Is it possible to throw die and get forty sixes in a row? • 666666666……66666666 • But the chances of doing this experimentally are very small. • But if we allow the probabilities of each results to vary then a witness becomes more likely • p1=p2=p3=p4=p5=0.001 and p6=0.995 • So why not evolve the probabilities (the system) to give the best chances of answering the question you want. • Possibility (hazard identification) and reliability/likelihood are different things.

  8. Warping Systems II-a Want test datum for hard to reach part if the system

  9. Warping Systems II-b Find test datum for stretched system

  10. Warping Systems II-c Now collapse back to original system and “drag” the test data back with you.

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