In the nearly three years since 9/11,Americans have become better protected against terrorist attack. Some of the changes are due to government action, such as new precautions to protect aircraft. A portion can be attributed to the sheer scale of spending and effort. Publicity and the vigilance of ordinary Americans also make a difference.

But the President and other officials acknowledge that although Americans may be safer, they are not safe. Our report shows that the terrorists analyze defenses. They plan accordingly.

Defenses cannot achieve perfect safety. They make targets harder to attack successfully, and they deter attacks by making capture more likely. Just increasing the attacker's odds of failure may make the difference between a plan attempted, or a plan discarded. The enemy also may have to develop more elaborate plans, thereby increasing the danger of exposure or defeat.

Protective measures also prepare for the attacks that may get through, containing the damage and saving lives.

Terrorist Travel

More than 500 million people annually cross U.S. borders at legal entry points, about 330 million of them noncitizens. Another 500,000 or more enter illegally without inspection across America's thousands of miles of land borders or remain in the country past the expiration of their permitted stay. The challenge for national security in an age of terrorism is to prevent the very few people who may pose overwhelming risks from entering or remaining in the United States undetected.³¹

In the decade before September 11, 2001, border security-encompassing travel, entry, and immigration-was not seen as a national security matter. Public figures voiced concern about the "war on drugs," the right level and kind of immigration, problems along the southwest border, migration crises originating in the Caribbean and elsewhere, or the growing criminal traffic in humans. The immigration system as a whole was widely viewed as increasingly dysfunctional and badly in need of reform. In national security circles, however, only smuggling of weapons of mass destruction carried weight, not the entry of terrorists who might use such weapons or the presence of associated foreign-born terrorists.

For terrorists, travel documents are as important as weapons. Terrorists must travel clandestinely to meet, train, plan, case targets, and gain access to attack. To them, international travel presents great danger, because they must surface to pass through regulated channels, present themselves to border security officials, or attempt to circumvent inspection points.

In their travels, terrorists use evasive methods, such as altered and counterfeit passports and visas, specific travel methods and routes, liaisons with corrupt government officials, human smuggling networks, supportive travel agencies, and immigration and identity fraud. These can sometimes be detected.

Before 9/11, no agency of the U.S. government systematically analyzed terrorists' travel strategies. Had they done so, they could have discovered the ways in which the terrorist predecessors to al Qaeda had been systematically but detectably exploiting weaknesses in our border security since the early 1990s.

We found that as many as 15 of the 19 hijackers were potentially vulnerable to interception by border authorities. Analyzing their characteristic travel documents and travel patterns could have allowed authorities to intercept 4 to 15 hijackers and more effective use of information available in U.S. government databases could have identified up to 3 hijackers.³²

Looking back, we can also see that the routine operations of our immigration laws-that is, aspects of those laws not specifically aimed at protecting against terrorism-inevitably shaped al Qaeda's planning and opportunities. Because they were deemed not to be bona fide tourists or students as they claimed, five conspirators that we know of tried to get visas and failed, and one was denied entry by an inspector. We also found that had the immigration system set a higher bar for determining whether individuals are who or what they claim to be-and ensuring routine consequences for violations-it could potentially have excluded, removed, or come into further contact with several hijackers who did not appear to meet the terms for admitting short-term visitors.³³

Our investigation showed that two systemic weaknesses came together in our border system's inability to contribute to an effective defense against the 9/11 attacks: a lack of well-developed counterterrorism measures as a part of border security and an immigration system not able to deliver on its basic commitments, much less support counterterrorism. These weaknesses have been reduced but are far from being overcome.

Recommendation: Targeting travel is at least as powerful a weapon against terrorists as targeting their money. The United States should combine terrorist travel intelligence, operations, and law enforcement in a strategy to intercept terrorists, find terrorist travel facilitators, and constrain terrorist mobility.

Since 9/11, significant improvements have been made to create an integrated watchlist that makes terrorist name information available to border and law enforcement authorities. However, in the already difficult process of merging border agencies in the new Department of Homeland Security-"changing the engine while flying" as one official put it³⁴-new insights into terrorist travel have not yet been integrated into the front lines of border security.

The small terrorist travel intelligence collection and analysis program currently in place has produced disproportionately useful results. It should be expanded. Since officials at the borders encounter travelers and their documents first and investigate travel facilitators, they must work closely with intelligence officials.

Internationally and in the United States, constraining terrorist travel should become a vital part of counterterrorism strategy. Better technology and training to detect terrorist travel documents are the most important immediate steps to reduce America's vulnerability to clandestine entry. Every stage of our border and immigration system should have as a part of its operations the detection of terrorist indicators on travel documents. Information systems able to authenticate travel documents and detect potential terrorist indicators should be used at consulates, at primary border inspection lines, in immigration services offices, and in intelligence and enforcement units. All frontline personnel should receive some training. Dedicated specialists and ongoing linkages with the intelligence community are also required. The Homeland Security Department's Directorate of Information Analysis and Infrastructure Protection should receive more resources to accomplish its mission as the bridge between the frontline border agencies and the rest of the government counterterrorism community.