Michael Hayden, 69, served as the director of the National Security Agency from 1999 to 2005. After leaving the NSA, he served as director of the CIA from 2006 to 2009. Today he is a partner at the consulting firm Chertoff Group in Washington, DC.

SPIEGEL recently sat down with the former US Air Force general in Washington for a wide-ranging interview on revelations from the archive of former NSA contractor Edward Snowden, including allegations that the intelligence agency spied on the cell phone of German Chancellor Angela Merkel, that have been the source of significant trans-Atlantic tensions.

Hayden: I am very concerned. This may be the single greatest, most destructive effect from the last 10 months of what Mr. Snowden has revealed. The Internet was begun in the United States and it is based on American technology, but it's a global activity. We in the United States feel it reflects free people, free ideas and free trade. There are countries that do not want the Internet as we know it. Russia, China, Iran, Saudi Arabia. The Snowden revelations will now allow them to argue that we Americans want to keep a single, unitary Internet, because it just helps us spy. My fear is that the disclosures may have set a motion in progress that ends up really threatening the Internet as we know it.

SPIEGEL: It is not only the Russians and Chinese who use this argument, but also Americans like Facebook founder Mark Zuckerberg. He recently described the US government as a threat to the Internet.

Hayden: The more people like him say that, the more it indirectly strengthens these other arguments. The Russians and the Chinese aren't saying this to protect themselves against alleged American espionage. They are saying this because they don't like the Internet's freedom of speech. Their goal is to divide the Internet up into national domains and create barriers in cyberspace. That's the last thing Zuckerberg would want to have happen.

SPIEGEL: On the one hand, the United States promotes the Internet as a tool of freedom. On the other hand, it now appears to many people to be a tool of surveillance.

Hayden: I am quite willing to have a discussion about what my country has or has not done, but it has to be based on facts. Let me first point out that the NSA doesn't monitor what every American is doing on the Internet. The NSA doesn't check who goes to what websites. But you've got these beliefs out there now.

SPIEGEL: Your predecessor as head of the NSA, General Kenneth Minihan, compared the Internet with the invention of the atomic bomb. He said a new national effort should be dedicated to one single goal, "information superiority for America" in cyberspace. It looks like you've gotten pretty close.

Hayden: We Americans think of military doctrine and "domains" -- land, sea, air, space. As part of our military thought, we now think of cyber as a domain. Let me define air dominance for you: Air dominance is the ability of the United States to use the air domain at times and places of its own choosing while denying its use to its adversaries at times and places when it is in our legitimate national interest to do so. It's just a natural thing for him to transfer that to the cyber domain. I do not think it is a threat to world peace and commerce any more than the American Air Force is a threat to world peace and commerce.

SPIEGEL: But do you understand if people in other countries are concerned about one country trying to gain "superiority" over something transnational like the Internet?

Hayden: I certainly do, and I thoroughly understand that. Now, other countries are creating cyber commands, but we were first, public, and very forceful in our language. We are now accused of militarizing cyberspace. Around the time US Cyber Command was created, McAfee did a survey of cyber security experts around the world. One of the questions they asked of them was, "Who do you fear most in cyberspace?" The answer for the Americans was the Chinese. With the plurality of people around the world, it was the Americans.

SPIEGEL: Britain's GCHQ intelligence agency speaks of "mastering" the Internet, and in another document, NSA officials say they want to "own" the Internet. Is it time for a new approach?

Hayden: Maybe not for a new approach but certainly for a new vocabulary. We might have been a bit too dramatic in our language.

SPIEGEL: So it was just a language issue?

Hayden: No. But nations conduct espionage. Mine, too. We're very good at it. We spend a lot of money at it: more than $50 billion a year for the national effort. The problem is that since the Snowden revelations we're talking about American espionage, British espionage and Australian espionage, but not about Chinese or Russian espionage. As powerful as those three I mentioned are, they actually self-limit. They are also the most transparent. I would offer you the view that European parliamentarians now know far more about the National Security Agency than they will ever learn about their own nation's intelligence services.

SPIEGEL: Isn't there a disconnect between your country being the champion of the Internet as a symbol of freedom and the goal, as the NSA puts it, of owning the Internet?

Hayden: I wouldn't say disconnect. But there is a dissonance. During the Arab Awakening my government was actually giving money to NGOs to pass out software to citizens in Arab countries to protect their anonymity. You've got conflicting values, but a state has a legitimate interest in freedom, and a state has a legitimate interest in security.

SPIEGEL: It has been almost a year since Snowden left Hawaii. What has he changed?

Hayden: There are three or four effects. We do this, like other countries, for legitimate reasons, and it's harder to do this now with what has been made public, legitimate intelligence targets. It has become harder for American services to cooperate with friendly services with common goals. What foreign service would want to cooperate with us, given our absolute seeming inability to keep anything secret? And then it really harmed American industry, and that's why you have the Mark Zuckerbergs of the world and the Eric Schmidts of the world expressing great outrage. They aren't doing anything for the American government that other companies do not do for their host governments when they receive a lawful request, but they've been singled out, and they have been unfairly harmed by this. And finally, it has poisoned relationships between people who really are friends.

SPIEGEL: Germany for example.

Hayden: The whole question about the chancellor has made this much more difficult. Although I'm not prepared to apologize for conducting intelligence against another nation, I am prepared to apologize for embarrassing a good friend. I am prepared to apologize for the fact we couldn't keep whatever it was we may or may not have been doing secret and therefore put a good friend in a very difficult position. Shame on us. That's our fault.

SPIEGEL: We didn't hear someone apologize officially.

Hayden: I'm prepared to apologize.

SPIEGEL: Is there any good reason for conducting surveillance against Merkel's mobile phone ?

Hayden: It's hard for me to answer as I'm not in the government. But leadership intentions are always a high priority, a foreign intelligence objective. In 1978, you've got US-President Carter wagging his finger at his intel people at the Camp David Accords between Egyptians and Israelis saying, "I want to know what Anwar al-Sadat and Menachem Begin think. I want to know what they think about me. I want to know what they think about each other. I want to know what in their heart of hearts they think about the agreement we've put on the table." How are you going to do that? I suspect you're going to conduct aggressive surveillance against their communications. Whether that circumstance applies to the chancellor is an entirely different question, but I would add that the chancellor's predecessor …

SPIEGEL: … Gerhard Schröder  …

Hayden: … conducted a whole variety of things that were kind of inconsistent with the American view of the world, which is not claiming the American view is right. We did the Iraq war with very different points of view. His approach to Russia was very different than the American approach to Russia, and then finally, this whole Gazprom billion-euro loan guarantee also raised questions, which might be answered by this kind of activity.

SPIEGEL: Would that justify surveillance of his cell phone?

Hayden: I am not going to make that conclusion. What I am going to say, though, is that you could see circumstances like that where that might make it more rather than less attractive to do. In 2008, when President Obama was elected, he had a BlackBerry. We thought, oh God, get rid of it. He said, "No, I am going to keep it." So we did some stuff to it to make it a little more secure. We're telling the guy who was going to soon be the most powerful man in the most powerful country on Earth that if in his national capital he uses his cell phone, his BlackBerry, countless number of foreign intelligence services are going to listen to his phone calls and read his e-mails. It's just the way it is.

SPIEGEL: The Germans are more sensitive when it comes to the issue of surveillance.

Hayden: I confess that we Americans underappreciated the impact of that not just on the chancellor but on the German population, and I mean this sincerely. Perhaps we underestimated the depth of feelings that the German people -- and again, not just the chancellor, but the German people, felt about this question of privacy, given their historical circumstances compared to our historical circumstances. At the Munich Security Conference it was clear to me that Germans regard privacy the way we Americans might regard freedom of speech or religion. Perhaps we did not appreciate that enough.

SPIEGEL: Do you think the president missed the chance to inform the chancellor about the facts when he visited her in Berlin last June?

Hayden: I don't know the facts of the case, but to be perfectly candid with you and your readers, the president promised to not surveil Angela Merkel. This was not a promise in perpetuity that no head of the German government would be surveilled.

SPIEGEL: Who makes the decision to monitor Schröder's or Merkel's cell phone? Did the White House know about it?

Hayden: Our government has made it clear that the president did not know and I will simply say if the president said he didn't know, then the president did not know, period. But it is not plausible that the White House didn't know. It's not plausible that the National Security Council didn't know. But this had not been a personal decision on the part of the president.