The legislation authorizing post-Sept. 11 intelligence reform — the Intelligence Reform and Terrorism Prevention Act of 2004 — was signed into law five years ago this week. We are often asked whether the new organizations, authorities and additional resources have made a difference. The answer is yes.

To be clear, the task of reinventing our intelligence structure and integrating the capabilities, cultures and information technologies of 16 diverse intelligence agencies is massive, and it is incomplete. Problems persist in our technologies, business practices and mind-sets. I have no illusions about how challenging they will be to overcome. But there is an ocean of difference between difficult and impossible.

While many successes must remain classified, there are things the public can and should know about changes that have been made and how we are directing our efforts and America's resources.

A prime example is the new level of cooperation among FBI, local law enforcement and U.S. intelligence agencies in the recent arrests of Najibullah Zazi and David Headley, Americans allegedly associated with foreign terrorist organizations who are charged with planning attacks in this country and overseas. In both cases, tips and leads were smoothly passed among those gathering information in this country and those gathering information overseas, including foreign intelligence services that provided information or responded to questions. These investigations connected the dots in exactly the ways the Intelligence Reform and Terrorism Prevention Act envisioned. However, as the case of Army Maj. Nidal Hasan, who has been charged with the Fort Hood, Texas, shootings, shows we must go even further in our efforts to turn intelligence into the knowledge needed to protect Americans.

Innovative use of information technology across agencies is enabling analysts to make use of the enormous amounts of data we are gathering and to distill insights that will help policy-makers in Washington and civil and military officers in the field. Thousands of analysts form groups spontaneously, in real time, on A-Space, post insights in Intellipedia, retrieve relevant analyses from the Library of National Intelligence and interact with the tribal database for Afghanistan. These tools, among others, ensure that each piece of analysis takes advantage of work being done and that new insights are immediately available to those who need them.

Close collaboration among collectors and analysts utilizing human, satellite and signals intelligence produced key evidence of a prospective covert uranium enrichment facility in Iran. Teamwork among different agencies in the United States and partners abroad just last week led to the interdiction of a Middle East-bound cargo of North Korean weapons.

Initiatives that will make us even more effective are moving forward. More than 6,000 intelligence officers are now "joint duty" qualified, and another 5,000 are gaining interagency experience. Cross-agency teams are making steady improvements in our administrative information systems so that we can better manage our human and financial resources; the Intelligence Advanced Research Projects Activity is funding high-risk, high-payoff projects in quantum computing, identity recognition, computer network intelligence and other areas that will benefit many agencies down the line.

The new National Intelligence Strategy provides the blueprint for further improvement in effectiveness. All U.S. intelligence organizations collaborated this year to articulate our shared mission and objectives. The strategy puts unprecedented focus on cybersecurity, counterintelligence and the impact that problems such as pandemic disease, climate events, failed states and scarce natural resources have on global stability. It recognizes the role of intelligence in identifying common interests and defusing threats in such issues as energy, trade, drug interdiction and public health.

Like our armed forces and first responders, intelligence professionals are on the front lines in defense of this country. Their operations are already collaborative between and across agencies to an extent that was unheard of five years ago. Continued commitment and investment in this reform are vital. If we become complacent now, or pessimistic about future progress, and revert to stovepipes and turf battles, full transformation will never be achieved.

Continued reform will also not be possible without a full commitment from the inside. Every intelligence agency, director, manager and employee has a role in breaking down the remaining impediments to integration. I find that the overwhelming majority of intelligence officers recognize the importance and benefits of integration. While taking pride in their individual skills and agencies, they are eager to cooperate with others to accomplish the common mission. This is most true in the field — overseas and closer to home at fusion centers in Los Angeles and Chicago.

It has been famously argued that information is power and, therefore, should never be shared. The Sept. 11 attacks showed the fatal flaws in that logic. Our nation is becoming safer every day because we are aware that information increases in power only when it is shared. Our mission is a fully integrated intelligence community, and there is no turning back. My most urgent priorities are to permanently instill this new culture and to use every tool at my disposal — from joint duty to recruitment and communications — to build a generation of intelligence leaders for whom this culture is business as usual.

Dennis C. Blair is director of national intelligence. He wrote this commentary for The Washington Post.