Stressing and stretching
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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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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

Need only fill up buffer and then feed the server as it dispatches


Smarter DoS: Low Rate Attack

Server

Need only fill up buffer and then feed the server as it dispatches


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.


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.


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.


Warping Systems II-a

Want test datum for hard to reach part if the system


Warping Systems II-b

Find test datum for stretched system


Warping Systems II-c

Now collapse back to original system and “drag” the test data back with you.


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