Answering Al Qaeda

More than five years have passed since terrorism struck our country. Some say this is no surprise. After all, since then we have reorganized the government and created an agency dedicated to protecting us from another attack — the Department of Homeland Security. We have spent billions of dollars to better secure potential targets. We have dislodged Al Qaeda from its sanctuary in Afghanistan, and killed or captured scores of its followers around the globe.

Perhaps another strike on the country is unlikely, but I very much doubt it. From everything we know, Al Qaeda is as determined as ever to attack us at home, and it remains as capable as ever of doing so. While many of its operatives have been killed or captured since 9/11, the supply of young people who are willing and even eager to attack Americans seems limitless.

Our disastrous misadventure in Iraq has only increased that desire. Al Qaeda has reconstituted itself in Pakistan and is trying to reclaim Afghanistan. It is only marginally harder for terrorists to enter the United States now than it was before 9/11, and once they’re inside our borders the potential targets are infinite. Many of those targets are more secure today, but not to the degree they should be.

As if we needed a reminder that another 9/11 remains a real threat, let’s look at what happened just last week: Another chilling videotape from Osama bin Laden’s top deputy, Ayman al-Zawahri, appeared. The State Department acknowledged that attacks worldwide are on the rise. Five Britons with links to Al Qaeda were sentenced for plotting spectacular attacks in their country, highlighting the danger of “homegrown” terrorism here as well. And the former C.I.A. director George Tenet maintained that “Al Qaeda is here and waiting.”

We can never make ourselves invulnerable to terrorism. But certain steps would reduce our vulnerability to as close to zero as possible. Among those steps should be these:

Aviation

• Install “backscatter” machines (being tested) at every airport checkpoint in the country. These X-ray-like devices reveal guns and knives on passengers’ bodies or in their clothes that screeners often miss.

• Deploy at every airport checkpoint multiview X-ray machines that automatically rotate passengers’ carry-on bags so screeners can see them from every angle, improving their ability to spot concealed weapons.

• Install explosive-detection technologies at every airport checkpoint to spot trace explosives on passengers’ bodies and bags.

• Redouble efforts to develop technologies to detect liquid explosives.

• Inspect 100 percent of the cargo in passenger planes.

• Ensure that only Americans work at airports and that all workers are screened each time they approach a checkpoint, hangar, tarmac or similar area.

Seaports

• Inspect (ideally before they reach our shores) 100 percent of the cargo ships bound for United States ports for radiation to detect any concealed weapon of mass destruction.

Borders

• Triple the number of Border Patrol Agents, and supplement their efforts with sensors, cameras and unmanned aerial vehicles that are actually deployed and work.

• End the visa-waiver program, which enables terrorists to reduce their chances of being caught at legal ports of entry by using passports from visa-waiver countries like Britain and France to bypass the scrutiny that visa applicants have to undergo.

• Rededicate the Department of Homeland Security to the goal of adding an exit feature to the automated border entry system, so we know whether terrorists who slipped into the country have left.

Mass Transit

• Provide money for mass transit authorities to deploy armed police patrols, bomb-sniffing dogs and technology, surveillance cameras, public awareness campaigns and random bag searches permanently, not simply during heightened states of alert.

Intelligence

• Ensure that the intelligence community provides the Department of Homeland Security with any information concerning threats against the country and that the department disseminates that information quickly to relevant state and local government officials, first responders and private businesses.

Preparedness

• Ensure that, in the event of an attack, there is a clear chain of command among the federal, state and local governments; interoperable communications among first responders; supplies of food, water and medicine; and clear, workable evacuation plans.

It is only a matter of time before another catastrophic attack is attempted. The sooner we take the steps outlined above the less likely such an attempt is to succeed.

Clark Kent Ervin, the former inspector general of the Department of Homeland Security, and the director of the Homeland Security Initiative at the Aspen Institute and the author of Open Target: Where America Is Vulnerable to Attack.