On the wall at the front of a basement room here, Agnes Meyder is explaining a complicated diagram depicting enzymes and cell walls, an example of a cancer database with which she is illustrating a talk on her field of bioinformatics.

An hour later, and it is sentences that are being diagrammed, as Cäcilia Zirn describes sentiment analysis is allowing computers to learn whether human writings – in online reviews or Twitter posts, for example – are positive or pissed-off.

These aren’t stereotypical subjects for hackers, but this is the Chaos Computer Club (CCC) Congress and Meyer and Stilz are hackers indeed, part of a loose 22-year-old group of women within the club called the Haecksen (a pun on the German word for witch).

There is no immediate agenda here, other than to meet each other, share coffee and ideas, and let other women know there are others like them. But it’s clear the women in this room have been forced to think about – and perhaps defend — their identity as hackers more than many of the hundreds of men sitting in front of screens and keyboards in the conference outside.

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