Here are two credible threats to global systems: a massive cyber attack that could spread to the rest of world and interfere with SCADA systems everywhere and carbon whiskers that could short out power transmission systems.

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Speculation has spread over possible motives for the attack - including the possibility that a competitor is looking to set up a rival site on the network.

BBC: Silk Road screenshot

The malware was employed in an attack against Apple and other companies, and was spread through a website for software developers.

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The attack on Spamhaus was so big because the organization had spread its infrastructure over 20 countries.

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That whole area is very spread out, so they would need to conduct a massive, co-ordinated attack on several facilities all at the same time and the Saudis seem to be alert to this ambition.

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If the millions of internet-connected Macs are left open to attack then this increases the chance that an effective Trojan or piece of spyware will reach critical mass and spread rapidly, and it also increases the incentive for a bright programmer to write Mac-specific malware that could affect me.

BBC: Steve Jobs waits on stage, AP