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Ready, aim ... exploit! Experts calculate exact moment to launch that precious 0-day weapon

Don't fire until you see the whites in their silicon dies

By Richard Chirgwin, 14 Jan 2014

There's a right time and a wrong time to exploit a vulnerability – and according to researchers from the University of Michigan, that's something that can be worked out ahead of time.

According to this paper Timing of cyber conflict, available from PNAS, knowing exactly when to launch a digital assault is something that can be calculated from the following information:

  • Persistence – “the probability that if you refrain from using it now, it will still be useable” in the future. In other words, if you have a zero-day up your sleeve (and bear in mind they are worth a lot of money), do you use it now, or hope that it won't get patched before you want to use it?
  • Stealth – “the probability that if you use it now it will still be usable” in the future. In other words: can you deploy an attack based on a vulnerability, without being detected?
  • Threshold – What conditions would lead you to use a particular cyber attack vector?

The findings may not be particularly Earth-shattering to seasoned infosec professionals, but they can be taken as a neat summary of considerations IT security types must ponder every day.

As the authors say: “The heart of our model is the trade-off between waiting until the stakes of the present situation are high enough to warrant the use of the resource, but not waiting so long that the vulnerability the resource exploits might be discovered and patched even if the resource is never used.”

The writers, Robert Axelrod and Rumen Iliev of the Ford School of Public Policy at the University of Michigan, then test the model against historical examples such as Stuxnet; Iran's attack on Saudi Aramco; Chinese cyber-espionage; and China's restriction of rare earth exports.

In the Stuxnet case, they say, the attack used had low persistence because it depended on a combination of vulnerabilities: the use of USB keys to deploy the worm (which could have been banned at any time by the target, the Iranian nuclear enrichment plant at Natanz), the spread technique (via a shared printer), and the worm's privilege escalation. However, because the attack was stealthy, its designers were confident that it would evade detection (as it did, for 17 months), so they decided that it was better to deploy sooner rather than later.

Similarly, they say, China's apparently-frequent cyber-espionage seems to be predicated on the belief that their attacks have low persistence (they'll get patched soon) but may have reasonable stealth.

While none of this will come as a surprise to experts in the field, the aim of the Axelrod-Iliev paper seems to be to help policy-level people understand the cyber-attack landscape with a minimum of technical grasp. ®

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