It's great to be back in Boston. John F. Kennedy once described Washington as "a city of Southern efficiency and Northern charm." I think he was a bit hard on the North. There's something comforting in being back among Boston's many charms. Passing a Dunkin' Donuts on every corner. Seeing the glares directed at those who dare to wear Yankee caps. Hearing every fifth word modified by "wicked."

Today I want to talk about the FBI's role in the relationship between freedom and security-in particular, the balance of national security and civil liberties. I can think of no more fitting place than the John F. Kennedy School of Government. President Kennedy was one of freedom's greatest champions, and one of freedom's greatest orators.

Exactly 46 years ago tomorrow, President Kennedy delivered a speech to the American Newspaper Publishers Association. He discussed the delicate balance between the need to keep the public informed through freedom of the press and the need to keep the public secure through limiting the amount of information made available to America's enemies. America was deep in the Cold War, facing unprecedented threats. In President Kennedy's words:

"Our way of life is under attack. Those who make themselves our enemy are advancing around the globe. The survival of our friends is in danger."

Two generations later, we find ourselves in the midst of another fierce struggle. Once again, our way of life is under attack and our enemies are advancing around the globe. And once again we must confront the question of how to properly balance the protection of American lives with the protection of American liberties.

The FBI's mission is to protect both. And we do.

Before I discuss what the FBI is doing to protect our freedom, let me first address the gravest threat to our way of life—the threat of terrorism.

Since the September 11 attacks, the FBI has worked closely with the law enforcement and intelligence communities to prevent another attack. We have made substantial progress.

Working together, we have dismantled terrorist camps overseas and detected terrorist cells here at home. We have disrupted terrorist communications and finances. We have diminished the leadership and command structures of groups such as al Qaeda. And so far we have prevented another attack on our homeland.

Yet we are still not safe. I do not say this to be an alarmist. The reality is that although we have grown accustomed to feeling secure on our own soil, terrorists have attacked other nations, and they still want to attack us. We cannot afford to become complacent. Terrorists are not likely to go into another line of work.

Recent intelligence underscores al Qaeda's resilience. They are seeking out new sanctuaries for recruiting and training. They are promoting from within. And they are using seasoned operatives to plan attacks around the world.

No country or community is immune. The threat stretches from Bali all the way to Boston. Remember, the morning of September 11, 2001, 10 of the hijackers passed through Logan Airport.

Terrorists do not need massive armies to cause massive carnage, but only a few faithful followers. They no longer need a single leader preaching a message of hate, but an ideology they can spread on the Internet. They no longer need al Qaeda subsidies or advanced technology, but a small amount of money they can raise themselves, and bombs they can detonate with their cell phones.

Terrorists have global ambitions and global reach. One of the unintended consequences of damaging al Qaeda's hierarchy is that its remaining members and its newest acolytes are dispersed across the globe. Al Qaeda is no longer just an organization; it is a movement. Its followers may have no formal affiliation with al Qaeda, but may be inspired by its message of violence.

We are now worried not just about new sanctuaries emerging overseas, but also about pockets of concern in our own neighborhoods. For instance, we have already discovered homegrown cells-from Ohio to Oregon, and from Lackawanna, New York to Northern Virginia.

The FBI's mission is to protect America from these threats, and from many others, including threats to civil rights and civil liberties. Some have suggested there is an inherent conflict between protecting national security and protecting civil liberties.

I disagree.

We have a right to privacy. But we also have a right to ride the train to work without bombs exploding.

We in the FBI are sworn to protect both national security and civil liberties. It is not a question of conflict; it is a question of balance.

If we safeguard our civil liberties but leave our country vulnerable to a terrorist attack, we have lost. If we protect America from terrorism but sacrifice our civil liberties, we have lost. We must strike a balance.

This is not a new concept. We have all heard Ben Franklin's assessment: "They who would give up an essential liberty for temporary security deserve neither liberty or security." But as the guardian of both, the FBI is in the center of this debate. So how do we try to guarantee both? We struggle with this question every day.

Let me give you a hypothetical scenario. Let's say that while investigating last year's plot to blow up airliners bound for the United States, British authorities discovered the terrorists had called a phone number in the United States.

Our immediate concern would be to find out who the British terrorists had been talking to and why. So we would check that U.S. phone number against our databases. Here we must walk the line between investigating a possible connection to a plot in the United States, and respecting privacy. Yes, it's possible the terrorists had just dialed an innocent acquaintance, but can we take that risk? Would you want us to take that risk? And what if we are wrong?

Now let's say we discover the phone number is registered to a suspected terrorist. What should we do next?

In the post-9/11 world, we cannot afford to let any counterterrorism lead go unaddressed. The next logical step is to find out who else the U.S. subject has been talking to. So we would use a national security letter to obtain his phone records. But this is typically where privacy concerns again arise.

The subject might have called many numbers that have no connection whatsoever to terrorism. He might have called to order a pizza, or to request a cab, or to chat with a co-worker. But on the other hand, he might have also called a terrorist associate.

If we look at who the subject called, we may be criticized for accessing information about innocent Americans. But if we do not take a closer look by examining those phone records, we risk missing a key piece of evidence. And should an attack occur, we would most certainly be condemned—and rightly so—for not connecting the dots that could have foiled that attack.

Here, it is important to remember three things. One, communications are the lifeblood of terrorism. Two, in my example, we are not accessing the content of those phone calls, just the record that the phone calls occurred. And three, we can quickly exclude all the unrelated phone numbers, and focus only on those that raise red flags. From there, we can start to piece together the puzzle, bit by bit, without knowing what picture will eventually emerge.

I pose this as a hypothetical example because I cannot discuss the details of ongoing investigations. Suffice it to say, many of the real scenarios we investigate are not far from this example. Often what they have in common is a potentially serious threat, limited intelligence, and a limited time frame within which to act.

With each unique investigation, we wrestle with the same questions. Have we struck the right balance between security and freedom? Did we take every reasonable step? What if we didn't peel back that last layer that would have revealed a terrorist plot?

Unfortunately, our work is not like an episode of "Law & Order," where one clue leads effortlessly to the next, and a complex investigation can be wrapped up and successfully prosecuted inside an hour.

Intelligence is not smooth. Most often, it is piecemeal—a name here, a phone number there. Dame Eliza Manningham-Buller, the former head of Britain's domestic intelligence agency, MI5, puts it this way:

"Often difficult decisions need to be made on the basis of intelligence which is fragmentary and difficult to interpret…some is gold, some dross and all of it requires validation, analysis and assessment. When it is gold it shines and illuminates, saves lives, protects nations and informs policy."

We in the FBI are looking for the gold amid the dross. Our focus is on obtaining that information which helps us protect America. We ensure that we collect intelligence appropriately in three ways: through training, through oversight, and through adherence to the law.

First, training. Before FBI agents receive their guns and badges, they go through 21 weeks of rigorous training at our academy. They take courses not just in conducting surveillance and interviewing witnesses, but in lawfully opening investigations and gathering evidence. They learn not just the technique of making an arrest, but the legal basis for doing so, and the constitutional protections afforded to each suspect.

And to make sure they fully understand the magnitude of their oath to defend the Constitution, every new FBI agent visits the Holocaust museum, to see for themselves the horror and injustice that result when law enforcement becomes a tool for oppression.

This training carries through to every investigation. Agents adhere to federal statutes, the Attorney General Guidelines, and above all, the Constitution. They use a range of investigative tools. As was the case in our hypothetical example, one primary tool is the national security letter, which has been the subject of debate in recent weeks. So let me take just a moment to address the NSL issue.

I am the first to admit that the FBI fell short in its compliance with NSL statutes. With the help of the inspector general, we identified what happened and how, and we have taken steps to correct it. But I will also note that the inspector general concluded that none of these violations was intentional. Furthermore, the inspector general agreed with our assessment that NSLs are a critical investigative tool, and that they have been invaluable to many national security investigations.

The NSLs are a good example of another built-in protection, and that is transparency. The FBI is subject to substantial oversight, both internally and externally. More often than not, we are the first to identify our mistakes. But if not, we can depend on the wider safety net of the Inspector General, the Congress and the American public. It is to them that we are accountable, and it is from them that we receive substantial scrutiny.

We welcome this scrutiny, painful though it sometimes is, because we understand that our ability to protect the American people depends in large part on the people's ability to trust the FBI. We are servants of the people, and guardians of the Constitution. There is not one FBI employee who bears this responsibility lightly.

And what many people don't know is that we often go above and beyond what the law requires in order to fully protect our civil liberties.

For example, we have been well ahead of the curve in conducting privacy impact analyses for national security databases—not because we were required to, but because we take seriously our obligation to protect privacy.

And we have a Privacy and Civil Liberties Unit at FBI Headquarters. This unit works to ensure we have the right balance between our operations and our civil liberties obligations.

I spoke earlier about the current and emerging threat landscape—the intersection between crime and terrorism, between international plots and homegrown cells, between ancient hatreds and modern technology.

The scope of these threats has led some to say the FBI is not well-equipped to be both a law enforcement and an intelligence agency. These critics have called for a separate agency to be established along the lines of Britain's MI5.

While this is a system that works well in Britain, it would be a mistake here in the United States. It would do a disservice to the American people. The FBI is uniquely situated within the American system to address these threats precisely because it is a national security agency with law enforcement powers.

Some still think of the FBI as traditional crime-fighters—and indeed, criminal investigations have been our bread and butter for almost 100 years. But every single agent will tell you that intelligence contributes to every investigation, from criminal to cyber to counterterrorism.

Intelligence is nothing new to the Bureau. Intelligence is how we fought Nazi spies during World War II, Soviet espionage during the Cold War, and organized crime in the seventies and eighties. And it is how we are fighting terrorism. We have built on our foundation and adapted our intelligence capabilities so we can target today's threats.

Since September 11, we have hired thousands of analysts and translators. We established field intelligence groups in every FBI field office. Our agents and analysts work side-by-side in a joint facility with CIA and DHS personnel. We are fully integrated in the intelligence community under the director of national intelligence. Intelligence is now woven into every single investigation and operation, whether in Massachusetts or in Malaysia.

We cannot forget that terrorists operate at every level—local, regional, and global. But so does the FBI. We have offices in nearly 60 foreign countries. We work side by side with our state, local, and international counterparts. We collaborate on cases that cross jurisdictional boundaries, whether those boundaries are state lines or international borders.

Proponents of a separate domestic intelligence agency see a dichotomy between intelligence operations and law enforcement operations. The reality is that the two functions are synergistic in the fight against terrorism.

Because the FBI can do both, we can sit at one table and discuss the intelligence we are collecting-as well as what we should do with that intelligence. We can analyze whether it makes more sense to let an intelligence operation play out or to make arrests and begin prosecutions.

Establishing a separate agency to collect intelligence, and then pass it to law enforcement for action, would be counterproductive.

It's also worth noting that a separate intelligence agency would not possess the intrinsic responsibility to protect civil liberties that is part of the FBI's DNA. As President Kennedy pointed out in his speech 46 years ago, "There is little value in insuring the survival of our nation if our traditions do not survive with it."

The FBI's mandate to uphold the Constitution and protect civil rights and civil liberties is not a burden. It is what makes us better.

We understand the arguments of our critics, because when it comes to civil liberties we share common ground. Their job is to speak out because they believe deeply that our liberties are precious, and must be guarded. So do we. Part of our job is to investigate violations of civil rights and civil liberties. But another part of our job is to protect lives. These dual responsibilities make our task more complex, and put us squarely in the middle of the national security and civil liberties debate.

As we work together to strike the right balance, let us not underestimate the threat we face. We in the FBI would love nothing more than to reach the day when we can shut down our Counterterrorism Division. But the reality is that the terrorist threat will be with us for a long time to come.

The FBI has a desire and a duty to protect you from those threats. We and our partners are the last line of defense standing between America and the next September 11.

In his inaugural address, President John F. Kennedy said, "In the long history of the world, only a few generations have been granted the role of defending freedom in its hour of maximum danger." President Kennedy went on to say, "I do not shrink from this responsibility—I welcome it."

We, too, do not shrink from the responsibility of defending our freedom in its hour of danger. We welcome it. Like those before us, we will be judged by future generations on whether we succeed.

History will determine not just whether we defeat terrorism, but also whether we safeguard the liberties for which we are fighting, and maintain the trust of the American people. We know that if we win one struggle at the expense of the other—either way—we will have lost on both counts. In the fullness of time, I believe future generations will look back and judge that the FBI accomplished both missions.

It is our duty. It is our calling. And more than that, it is our privilege to serve and protect you.