How Wikileaks became a whistleblowers' haven

The release of 90,000 leaked US intelligence documents about the war in Afghanistan has thrown Wikileaks into the spotlight as never before. But how do you go about putting top secret documents online without getting caught?

What is Wikileaks?                

In 2006 a loose association of anti-censorship activists, lawyers and internet experts realised that the combination of the internet and sophisticated new anonymity tools could create a whistleblowers' haven where sensitive documents could be posted without fear of reprisal.

Their idea was that posting leaked documents could become as easy as posting an entry in Wikipedia – hence the name.

Wikileaks isn't a single organisation but a grouping of like-minded activists around the globe but is fronted in the main by Julian Assange, an Australian freedom-of-information advocate and former computer hacker. He and his colleagues – many of whom are lawyers – have taken advice on anonymising technology from experts such as Ben Laurie, pioneer of SSL – the "secure sockets layer" that keeps web transactions secure.

What provides anonymity for the whistleblower?

Despite its anti-authoritarian stance on censorship, Wikileak's main strength comes from a piece of technology developed by the Pentagon. A kind of network called The Onion Router – or Tor – enables users to post documents without fear of being traced.

A Tor network uses around 1000 volunteer servers around the world. To transmit a document, a whistleblower downloads a piece of software called a Tor client and uses it to inject the document into the Tor network. The document then bounces between Tor servers in a random manner, using layers of encryption to obfuscate its source address. Eventually it emerges at the destination – in this case Wikileaks.

To keep a step ahead of companies and governments who might want leaks taken down, Wikileaks is hosted in Sweden, where robust freedom-of-information legislation makes a takedown order unlikely. A similar site in transparency-friendly Iceland is being investigated. In addition, Wikileaks is mirrored at undisclosed locations around the world, so if it's taken down in one location, other sites can take over.

What sort of information has been leaked via Wikileaks?

The 90,000 documents relating to the Afghanistan campaign are just some of the 1.2 million documents posted to the site. Others have included claims of government corruption in Kenya, the design for the Hiroshima atom bomb and the military rule book for the Guantanamo Bay detention camp in Cuba; others still have included the financial accounts for a Masonic lodge and a detailed description of a sorority society's initiation ritual.

A recently released Wikileaks' video, Collateral Murder, showed a US army helicopter attack that killed 12 people, including two Reuters journalists, in Baghdad, Iraq, in 2007.

So can you post to Wikileaks without fear of being caught?

In short, no. As Tim Berners-Lee has said: "It is very difficult to make a foolproof anonymiser. Frankly, it's a bit hairy to be in that game."

The US military has arrested Bradley Manning, an intelligence analyst stationed in Iraq, on suspicion of leaking the helicopter footage. At this stage it is not clear whether he is thought to have been involved in leaking other documents. However, his arrest followed a tip-off from a contact, rather than the military tracing the source of Wikileaks posts.