A computer hacker with no permanent home, WikiLeaks founder Julian Assange has been described as highly intelligent, determined, intense and sometimes paranoid.
The 39-year-old Australian has made himself plenty of enemies, from the governments whose secret information he has revealed to his former colleagues he has alienated.
Now arrested by British police on a warrant issued in Sweden, where prosecutors want to question him about allegations of sexual crimes, Assange faces potential extradition.
Assange denies the allegations, which his supporters say are politically motivated.
U.S. authorities are also keen to find some way of charging him for his part in publishing classified information, although experts say it is far from clear whether he has himself committed a crime.
Like the WikiLeaks site itself, Assange has proved a divisive figure. Some see him as a hero, challenging censorship and the harbinger of a new age of openness. Others see him as a dangerous radical, wrecking the secretive norms of diplomacy, revealing what should not be revealed.
Whilst preaching the need for official openness, Assange himself is known for being highly secretive. It has been reported that he carries several mobile phones and a rucksack, moving from house to house and staying with friends from Iceland to Kenya.
Born in July 1971 in Townsville on Australia's Queensland coast, Assange has spent his entire life traveling. His parents worked in theater and were often on the road.
In his teens, he gained a reputation as a sophisticated computer programer before being arrested in 1995 and pleading guilty to hacking. He avoided prison on condition he did not reoffend and in his late 20s went to Melbourne University to study mathematics and physics.
He founded WikiLeaks in 2006, creating a web-based dead letter drop for would-be leakers.
Assange says he never wanted to become the public face of WikiLeaks. Initially, he says his plan was that the organization had no public face at all because I wanted egos to play no part in activities.
But he said this quickly became a distraction, with random individuals on the Internet claiming to represent the group.
Before the latest leak, the website had some five full-time staff, several dozen active volunteers and 800 part-time volunteers. Assange says he is effectively its publisher and editor-in-chief, although he still conducts his own research.
In the end, someone must be responsible to the public and only a leadership that is willing to be publicly courageous can genuinely suggest that sources take risks for the greater good, he told a web chat with Britain's Guardian newspaper.
In that process, I have become a lightning rod. I get undue attacks on every aspect of my life, but I also get undue credit as some kind of balancing force.
(Editing by Janet Lawrence)