A few years ago, Sarah Blow attended a networking event aimed at IT professionals. It was the first Geek Dinner, a gathering for anyone with an interest in IT and technology.

Blow was one of about 10 women in a group of 150. She was constantly asked if she worked in marketing. Others assumed she was someone's girlfriend. She wasn't - she's a software engineer, and by the end of the event she was frustrated enough to start her own group, and call it Girl Geeks.

"Girl geeks don't like this 90% male environment," she says on the London group's website. "There is too much politics, too many people saying 'I'm better than you'."

Men who attend Girl Geek dinners find out why being a woman in a male-dominated environment can be so difficult.

"Guys coming suddenly understand why females struggle," Blow says. "They don't understand the social pressures of being in a minority until they are [in] one."

Girl Geeks events are held so members can socialise and talk about technology in an informal environment. They give female IT staff a chance to be in the majority and talk to others in the same position as them.

The group does not exclude men - male geeks can attend if they are invited by a woman, and Blow emphasises how important it is that the push for diversity in IT is championed by everyone.

"We don't want to cut out the guys, because they are actually a way of helping to make change," she says.

"You can't assume that a few females can make the change - it has to be everyone. If it's not everyone, it's just a female issue.

"We aimed it at the girls because women in IT don't often get the opportunity to meet each other. I wanted to turn everything on its head - the concept of being in the majority as a female is almost unheard of in IT. And it plays about with the geek stereotype, which has tended to be a guy with greasy hair and glasses."

Women from all over the IT industry attend Girl Geek dinners, which are now held all over the world. There are 53 groups worldwide and eight in the UK. First and foremost, they exist as a chance to socialise with other female IT workers, provide support and help them learn from each other. But there are also indirect consequences of mobilising IT women into a group.

"The dinners are a social event, but as a result of going, members talk to the companies they work for about the concept. That in turn creates some institutional change," says Blow.