Hackers generally have a bad reputation. The name is associated with viruses, damaged hard drives and cyber-crime. But actually hacking means doing things with technology for which it was not originally intended.

The Chaos Computer Club, based in Germany, is an enormous organisation of hackers known for antics such as wiring up office buildings with lights to display text messages.

But they also regularly demonstrate serious security problems with existing technology which had been assumed safe. David Reid went to their most recent meeting in Berlin.

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