How many people had even heard of WikiLeaks a week ago? Or Julian Assange? And yet, seven days after the biggest intelligence leak of all time – the publication of over 75,000 files amounting to an entire history of the Afghanistan war – he is everywhere; in every newspaper, on every news broadcast, in what appears to be every country in the world. It's been an extraordinary week for WikiLeaks, which has seen the entrance on to the world stage of a remarkable new character: Assange, a man who, even friends and supporters admit, looks "a bit like a Bond villain".

Could it be the week that changed the war in Afghanistan? It's possible, if the revelations contained in the files swing popular and then political opinion. At the very least, they've triggered a whole new debate about the future course of the conflict. Because what the files revealed was the sheer scale and exhausting mundane detail of the everyday violence suffered by Afghan civilians, caused by coalition forces as well as the Taliban, as well as evidence of what may or not be double-dealing on the part of Pakistan government.

By last Wednesday, President Hamid Karzai of Afghanistan had branded Assange "irresponsible". And by Friday, the US defence secretary, Robert Gates, had accused him of "having blood on his hands". Their charge was that WikiLeaks has disclosed the names of Afghan collaborators who may now be subject to reprisals; that the information is unchecked; that some of it may be of dubious provenance, and that Assange seems to be accountable to no one.

Perhaps the most surprising and confusing aspect of all this is that Assange didn't leak the material. He was not the source for these files, he merely published them. Where once, the focus was on the whistleblower, it's now on the technological conduit by which the whistleblower can reach the world.

By the time I come to talk to Assange, his very last interview of the week, the backlash is in full swing. "Have you seen this?" he says waving a copy of the Times at me. "Have you seen how much bullshit this is? Have you seen page 13? Do you think I should call [the libel law firm] Carter-Ruck?

"It would be a bit silly for me but I'm tempted to. Just look at the headlines and the photo. What's the imputation?"

There's a photo of Assange below a headline that reads "'Taliban hitlist' row: WikiLeaks founder says he did right thing". And next to the photo, another headline reading "Named man is already dead." The imputation is quite clearly that Assange's actions have resulted in the man's death, although in the story itself it makes it clear that he actually died two years ago.

"Is it clear?" says Assange. "Let's see how much we have to read before we reach that information. It's not in the first paragraph, second, third, fourth, it's not in the fifth. It's not until the sixth paragraph you learn that."

The Times had splashed on its front page the claims that there are named Afghan sources in the files whose lives are now in danger. It's pure "self-interest", he says, designed to undermine the Guardian, the Observer's sister paper and one of three publications to publish stories based on the files, the others being the New York Times and Der Spiegel. "You can see that this is coming down from editorial, not up from journalism."

Maybe. Although it doesn't mean that there aren't hard questions to answer. What about these named sources? Might he have endangered their lives?

"If there are innocent Afghans being revealed, which was our concern, which was why we kept back 15,000 files, then of course we take that seriously."

But what if it's too late?

"Well, we will review our procedures."

Too late for the individuals, I say. Dead.

"Well, anything might happen but nothing has happened. And we are not about to leave the field of doing good simply because harm might happen … In our four-year publishing history no one has ever come to physical harm that we are aware of or that anyone has alleged. On the other hand, we have changed governments and constitutions and had tremendous positive outcomes."

If Afghan informers are at risk, he says, the fault lies squarely with the US military. "We are appalled that the US military was so lackadaisical with its Afghan sources. Just appalled. We are a source protection organisation that specialises in protecting sources, and have a perfect record from our activities.

"This material was available to every soldier and contractor in Afghanistan …It's the US military that deserves the blame for not giving due diligence to its informers."

Not everyone agrees. There's a school of thought, to which a leading article in the Times gave voice, that he is playing a dangerous game. He says he hasn't read it, so I quote a chunk: "The sanctimonious piety of the man is sickening."

"Oh sure," he says. "Because it would be better to be a ruthless media mogul just in it for the money. That would be then be acceptable. We can't actually have people doing something for moral reasons. It's only acceptable if we do it just for the money."

It is possible that this is part of it. When Julian Assange burst on to the world stage last week, people grappled to make sense of him, of WikiLeaks, of the new hybrid formed by old media – the Guardian, the New York Times, Der Spiegel – co-operating with a radical, activist, very new media, what the New Yorker described as less an organisation, more "a media insurgency".

It is no coincidence that last week marked WikiLeaks' most successful operation to date, and also the implementation of what is quite clearly a new media strategy. Not just its new step of co-operating with three international news organisations but also the decision, made over the past few months, for Assange himself to come out of the shadows and take up a public role as the WikiLeaks' front man.

"We started off like the Economist," he told a packed audience at the Frontline Club on Tuesday, meaning they retained complete anonymity. "We wanted to make the news, not be the news. But that produced extraordinary curiosity as to who we were ... this attempt not to be the news, made us the news."

This new openness seems designed to counter one of the greatest criticisms of the organisation: its lack of accountability. Because what this week has made clear is that it is no longer governments who can choose what to keep secret, it is WikiLeaks.

It feels like there's been some sort of revolution, I say to him, but one which the world is still struggling to understand. In reply, he deploys one of his deadly monotones: "We are creating a space behind us that permits a form of journalism which lives up to the name that journalism has always tried to establish for itself. We are creating that space because we are taking on the criticism that comes from robust exposure of powerful groups."

It is interesting that he phrases it this way because, as well as being a new and radically different model of what is and isn't possible in the news future, Assange himself is a curious hybrid.

His skills as a cryptographer led him to becoming one of the architects of the WikiLeaks model, but as Gavin MacFadyen, the director of the Centre of Investigative Journalism and a friend of his, points out, there's something almost old-fashioned about his particular brand of committed idealism.

"We don't really see people like him any more. In the 60s and 70s, they were around. Those who are totally committed and passionate about what they're doing. But not after 20 years of Thatcherism."

There was a video of Assange on the centre's website, and "our server crashed", says MacFadyen. "There's no doubt he's an inspirational figure." He is also "probably the most intelligent person I've ever worked with" and has an "unusual amount of self-confidence".

When you interview Assange, this seems like an understatement. He is at least five steps ahead. Probably more. But then, as he told the New Yorker, what appealed to him about computers was their austerity: "It is like chess – chess is very austere, in that you don't have many rules, there is no randomness, and the problem is very hard."

David Leigh, the Guardian's investigations editor who oversaw publication of the files, says Assange has the mentality of a hacker, "a distinct psychological genre". At times, he can seem almost autistic, although "he doesn't lack charm".

That is perhaps the most surprising thing about Assange. The first time I meet him, a fortnight before publication of the files, he's tense and edgy. With good reason, it turns out. The second time, after a speaking engagement at the Frontline Club, the journalists' club in West London he made his base for the week, he's like a man transformed: relaxed and clearly enjoying himself. He makes jokes. He even smiles. The third time, he looks simply exhausted. And yet, he's also still quite clearly up for taking on all-comers.

Vaughan Smith, the director of the Frontline Club, tells me that he's more or less subsisted on "two hours' sleep and two sandwiches". But then, there's something about Assange that if not superhuman, is almost as if sleep and food are mere technicalities that might concern the rest of us, but that he has found a way of simply dispensing with. Combat, intellectual combat, seems to be his stimulant of choice. It just fuels him.

When I try to question him about the morality of what he's done, if he worries about unleashing something that he can't control, that no one can control, he tells me the story of the Kenyan 2007 elections when a WikiLeak document "swung the election".

The leak exposed massive corruption by Daniel Arap Moi, and the Kenyan people sat up and took notice. In the ensuing elections, in which corruption became a major issue, violence swept the country. "1,300 people were eventually killed, and 350,000 were displaced. That was a result of our leak," says Assange. It's a chilling statistic, but then he states: "On the other hand, the Kenyan people had a right to that information and 40,000 children a year die of malaria in Kenya. And many more die of money being pulled out of Kenya, and as a result of the Kenyan shilling being debased."

It's the kind of moral conundrum that would unnerve most people, that made some wonder last week what the potential ramifications of the latest leak might be, but it is a subject on which Assange himself is absolutely clear: "You have to start with the truth. The truth is the only way that we can get anywhere. Because any decision-making that is based upon lies or ignorance can't lead to a good conclusion."

The other key thing about WikiLeaks is that it's internationalist in the true sense. "We do not have national security concerns. We have concerns about human beings," says Assange. And, with its servers located in different countries, and its headquarters nowhere, it raises intriguing questions about the future of nation states. WikiLeaks seems to be beyond the power of any of them, although Assange jumps on me pretty fast when I suggest as much.

"Of course not. We have had over 100 legal attacks. We have been victorious in almost every single legal attack. As far as nation states are concerned, we operate within the rule of law."

But it is an organisation that has been brilliantly constructed to get around such assaults, and with each release of information, it seems to evolve and grow stronger.

Even if it's not yet known, can't be known, what the long-term impact of this particular leak will be.

David Leigh describes Assange as "a mendicant friar of the electronic age". Like his organisation, he is global and rootless. And when he does sleep, it's usually on somebody else's sofa.

But Leigh also says "it's actually fairly irrelevant to talk about whether what Julian is doing is a bad thing or a good thing, because if he wasn't doing it, somebody else would".

Assange might be an arresting figure and WikiLeaks an extraordinary organisation, but they are manifestations of a phenomenon, he says, not its root cause.

"He's a function of technological change. It's because the technology exists to create these enormous databases, and because it exists it can be leaked. And if it can be leaked, it will be leaked."