Tweet if you 'like' terror

The head of the British security organisation GCHQ has warned that social networks such as Facebook and Twitter are in denial about the use of their sites by terrorists and criminals. And he is right: extremists of all kinds have indeed "embraced the web".

The battle for hearts and minds is a vital part of any conflict and social media is the perfect vehicle to disseminate propaganda to millions of people. It also allows small groups to exaggerate their influence.

Let's start with Islamic State. This media mujahideen - most of whom aren't even in Syria - wage hashtag campaigns on Twitter to generate internet traffic. They hijack other Twitter hashtags - such as #iPhone6 - to ensure their Islamist propaganda reaches more people and generates media interest. (They do this deliberately, directing tweets at the likes of CNN and the BBC.) They post real-time footage from the battlefield. They use social media "bots" to automatically spam platforms with their content.

Far-right movement Britain First has half a million Facebook "Likes", far more than the Tories or Labour Party. It produces and shares very good content online: campaigns about the armed forces, animal cruelty, child sex abuse. Things people with little interest in politics would share.

But, according to Hope Not Hate, an anti-fascist campaign group, these campaigns mask a more sinister motive. It argues that Britain First has been involved in intimidating Muslims, including invading mosques.

Whistleblower Edward Snowden has complicated the story considerably. Since his revelations there has been a significant growth in the availability and use of (usually free) software to keep internet users anonymous and guard their privacy. These tools are, and will continue to be, important tools for democratic freedoms, but along with journalists, human rights activists and dissidents, extremists will be their early adopters.

GCHQ director Robert Hannigan has urged the tech giants such as Facebook and Twitter to confront some "uncomfortable truths", accept that privacy is not an absolute right and to work closely with security services.

Censorship is not the answer. When IS was kicked off Twitter, some went to Diaspora, one of several new decentralised social media platforms run by users on their own servers, meaning, unlike YouTube or Twitter, their content is hard to remove.

The answer is found in riddle. The battle for ideas used to be waged from the air, through propaganda drops. But today it's more like hand-to-hand combat, played out across millions of social media accounts, 24 hours a day. Censorship doesn't work in this distributed, dynamic ecosystem. But the same tools used by extremists are free to the rest of us too. That gives all of us both the opportunity and responsibility to defend what it is we believe.

Unthinkable three years ago: you can now argue with an IS operative in Syria via Twitter from your own home.

The battle for ideas online can't be won, or even fought, by governments. It is down to us.