You could say Australian-born Julian Assange has swapped his long-time interest in network security flaws for the far-more-suspect flaws of even bigger targets: governments and corporations. Since his early 20s, he has been using network technology to prod and probe the vulnerable edges of administrative systems, but though he was a computing hobbyist first (in 1991 he was the target of hacking charges after he accessed the computers of an Australian telecom), he's now taken off his "white hat" and launched a career as one of the world's most visible human-rights activists.

He calls himself "editor in chief." He travels the globe as its spokesperson. Yet Assange's part in WikiLeaks is clearly dicier than that: he's become the face of creature that, simply, many powerful organizations would rather see the world rid of. His Wikipedia entry says he is "constantly on the move," and some speculate that his role in publishing decrypted US military video has put him in personal danger. A controversial figure, pundits debate whether his work is reckless and does more harm than good. Amnesty International recognized him with an International Media Award in 2009.

Assange studied physics and mathematics at the University of Melbourne. He wrote Strobe, the first free and open-source port scanner, and contributed to the book Underground: Tales of Hacking, Madness and Obsession on the Electronic Frontier.