George Habash, a militant and former secretary-general of the Popular Front for the Liberation of Palestine, once characterized terrorism as a "thinking man's game." Using mathematics, researchers at Stanford University's Center for International Security and Cooperation (CISAC) have made fighting terrorism a thinking man's game as well.

CISAC affiliate Lawrence M. Wein of the Graduate School of Business and CISAC Science Fellow Jonathan Farley are both applying mathematical models to homeland security problems, such as preventing a nuclear detonation in a major U.S. city and determining whether terrorist cells have likely been disrupted.

Wein, who teaches operations classes about different business processes used to deliver goods and services, has focused his research on bioterrorism and border issues. He has performed, he says, the first mathematical analyses of hypothetical botulism poisoning, anthrax outbreaks and smallpox infections.

"One overriding theme of my work is that all these homeland security problems are operations problems," said Wein, the Paul E. Holden Professor of Management Science. "Just as McDonald's needs to get hamburgers out in a rapid and defect-free manner, so too does the government have to get vaccines and antibiotics out and test the borders for nuclear weapons or terrorists in a rapid and defect-free manner."

In collaboration with Stephen Flynn of the Council on Foreign Relations, a nonpartisan research center, Wein recently has conducted research to improve security at U.S. borders and ports. Port security has received significant attention recently owing to the furor over Dubai Ports World's bid to manage six terminals at major U.S. harbors. The aim of Wein and Flynn's work is to prevent terrorists from bringing into the country a nuclear weaponbe it an atomic bomb or a so-called "dirty bomb," or conventional explosive packed with radioactive waste.

"Of all the problems I've studied, this is the most important because the worst-case terrorist scenario is a nuclear weapon going off in a major U.S. city and also it is the one the government has dropped the ball on the most," Wein said. "They have done a very poor job."

Instead of using the existing approach, where U.S. Customs actively inspects a minority of containers based on information from a specialized tracking system designed to identify suspicious containers, Wein and Flynn have recommended the government use a multi-layer, passive screening system for every container entering the country. Under their system, Customs would photograph a shipping container's exterior, screen for radioactive material and collect gamma-ray images of the container's contents. If terrorists shielded a bomb with a heavy metal such as lead to hide it from radiation detectors, gamma-ray imaging would allow inspectors to see the shielding and flag the container for inspection. Wein and Flynn believe this whole process would cost about $7 per container.

"Right now about maybe 6 percent of the containers are deemed suspicious and they will go through some testing and the other 94 percent of the containers just waltz right into the country without an inspector laying an eye on them," Wein said. "What we're proposing to do is 100 percent passive testing."

Wein's earlier work addressed a different threat: bioterrorism. In 2005, Wein revealed the nation's milk supply was vulnerable--a terrorist could potentially poison 100,000 gallons of milk by sneaking a few grams of botulinum into a milk tanker. Although the government and dairy industry have collaborated to intensify the heat pasteurization formula for milk, Wein is still pushing for additional botulinum testing, which he says would cost less than 1 percent of the cost of milk.

Wein also has used math to study smallpox outbreaks, the U.S. fingerprint identification system and U.S.-Mexico border security issues. Wein's congressional testimony on the fingerprint identification system in 2004 led to a switch from a two-finger system to a 10-finger system. His 2003 research on anthrax attacks resulted in a Washington, D.C., pilot program to use the U.S. Postal Service to distribute antibiotics throughout the capital after an outbreak. Seattle is now testing a similar program.

"In Washington, D.C., now, if there is a large-scale anthrax attack, postal workers will be the first to get their Cipro and, on a voluntary basis, they will go door-to-door distributing antibiotics," Wein said.

He said the common thread throughout his research is queuing theory, or the mathematical study of waiting lines, but he also draws upon mathematical epidemiology for his smallpox studies; air dispersion models for the anthrax model; supply chain management for the milk study; probability theory for the fingerprint identification system; and models for nuclear transport and detection for his work with containers.

From tainted lactose to lattice structures

While Wein is working on improving the government's counterterrorism systems, Jonathan Farley is working to figure out when terrorist organizations have been effectively disrupted. His mathematical model is designed to help law enforcement decide how to act once they have captured or killed a terrorist or a number of terrorists in a cell.

A professor at the University of the West Indies who will chair the Department of Mathematics and Computer Science there next year, Farley is on a one-year science fellowship at CISAC. In 2003, he co-founded Phoenix Mathematical Systems Modeling Inc., a company that develops mathematical solutions to homeland security problems.

He is using lattice theory--a branch of mathematics that deals with ordered sets--to determine the probability a terrorist cell has been disrupted once some of its members have been captured or killed.

"Law enforcement has to make decisions about what resources they should allocate to target different cells," Farley said. "The model should provide them with a more rational basis for allocating their scarce resources. ... It will inform you when you're making decisions about how much time and effort and how much money you're going to spend going after a particular cell."

While at Stanford, Farley hopes to unearth the perfect structure, mathematically speaking, for a terrorist cell--or in other words, a cell structure that is most resistant to the loss of members.

"If it's possible to determine the structure of an ideal terrorist cell, you can focus on a much smaller number of possibilities, because it makes more sense to assume the adversary is going to be smart rather than stupid," Farley said.

Farley has suggested it is possible Al-Qaida and other terrorist organizations already may have figured out the perfect structure for a terror cell by trial and error.

"I don't expect Osama bin Laden to be reading lattice theory in his caves in Afghanistan," said Farley. "But if it follows from the mathematics, perhaps heuristically, the terrorists will have come to the same conclusion--that this is the best way to structure a terrorist cell."

Although Farley acknowledges his model is not a panacea for terrorism, he hopes it will help reduce guesswork that might be involved in pursuing terrorists.

"It's not that I think mathematics can solve all of these problems," Farley said. "Because it can't. But it's better to use rational means to make decisions rather than guesswork."

John B. Stafford is a science-writing intern at Stanford News Service.

Ellen Johnson Sirleaf's inauguration as the president of Liberia marks a watershed in the country's tumultuous history.

Twenty-five years of misrule and civil war under Samuel Doe, Charles Taylor, and successive interim governments have left the country in ruins. Nearly 300,000 Liberians lost their lives, average income is one-eighth what it was in 1980, and large majorities of the population subsist in dire poverty.

Since United Nations and US troops ousted Taylor in 2003, a fragile peace has taken hold, supported by 15,000 UN peacekeepers. With free and peaceful elections under their belts, Liberians are feeling new optimism and hope. Markets here are bustling, stores are freshly painted and open for business, and newspapers and radios feature lively debate.

The new government is a clear break from a past characterized by rule by force, extensive corruption, and a culture of impunity. Sirleaf, the first African woman elected head of state, has been an outspoken champion of accountability, transparency, and good governance for decades, a stance that landed her in jail twice and was a hallmark of her opposition to past governments and campaign for the presidency.

Already change is underway. She has instituted a code of conduct and full financial disclosure for senior officials, and endorsed a program that will install internationally recruited financial controllers in several state enterprises and create a strong anticorruption commission. Her government plans to publish financial accounts on the Web, make it easier for whistleblowers to report infractions, and rewrite Liberia's outdated constitution to firmly establish participatory democracy, decentralize power, and install robust checks on the executive.

Recovery from deep conflict in Africa is not easy, but we know it is possible. Mozambique was destroyed by civil war in the 1980s, but its democratically elected government led the way to peace, stability, and a doubling of income in a dozen years. Sierra Leone suffered a blood bath in the 1990s, but the 1999 peace agreement and 2001 elections brought stability and economic growth of 7 percent a year. Rwanda's genocide was followed by a recovery that few could have imagined.

But Sirleaf faces a daunting task. Liberia's recovery will depend mainly on Liberians themselves, but it will require strong international support, just as in Mozambique, Sierra Leone, and Rwanda.

West Africa's civil wars have spawned widespread smuggling of diamonds, transshipment of drugs, and easy money laundering opportunities for global terrorist groups. Liberia's historic moment provides the U.S. administration a chance to show it is serious about supporting nascent democracies, creating stability in a volatile region, and providing economic opportunities for Africa's poorest countries.

First, the United States must continue its crucial role in the demobilization of combatants and commit to long-term rebuilding of Liberia's police and army. The new government must be able to maintain and enhance security to begin to recover.

Second, the administration should support rapid and comprehensive forgiveness of Liberia's debts, which were mainly undertaken and wasted by the rapacious Doe government. It makes no more sense to stick today's Liberians with the bill, including 20 years of accumulated interest, than to force today's Iraqis to pay Saddam Hussein's bills.

Third, and perhaps most urgent, Congress should approve supplemental funding of $50 million to $100 million to support the new government. Unfortunately, Congress recently cut the administration's initial request for Liberia, a short-sighted step that sent the wrong signal to a struggling democracy and old ally at a crucial turning point. These funds would build critical infrastructure, put kids back into schools, and continue vital training for security forces. It would give Liberians their best chance of securing peace and basic freedoms.

You're being watched...Congress will soon hold hearings on the National Security Agency's domestic spying program, secretly authorized by President Bush in 2002. But that program is just the tip of the iceberg.

Since 9/11, the expansion of efforts to gather and analyze information on U.S. citizens is nothing short of staggering. The government collects vast troves of data, including consumer credit histories and medical and travel records. Databases track Americans' networks of friends, family and associates, not just to identify who is a terrorist but to try to predict who might become one.

Remember Total Information Awareness, retired Adm. John Poindexter's effort to harness all government and commercial databases to preempt national security threats? The idea was that disparate, seemingly mundane behaviors can reveal criminal intent when viewed together. More disturbing, it assumed that deviance from social norms can be an early indicator of terrorism. Congress killed that program in 2003, but according to the Associated Press, many related projects continued.

The Defense Advanced Research Projects Agency runs a data-mining program called "Evidence Extraction and Link Discovery", which connects pieces of information from vast amounts of data sources. The Defense Intelligence Agency trawls intelligence records and the Internet to identify Americans connected to foreign terrorists. The CIA reportedly runs Quantum Leap, which gathers personal information on individuals from private and public sources. In 2002, Congress authorized $500 million for the Homeland Security Department to develop "data mining and other advanced analytical tools." In 2004, the General Accounting Office surveyed 128 federal departments and agencies to determine the extent of data mining. It found 199 operations, 14 of which related to counterterrorism.

What type of information could these mine? Your tax, education, vehicle, criminal and welfare records for starters. But also other digital data, such as your travel, medical and insurance records - and DNA tests. Section 505 of the Patriot Act (innocuously titled "Miscellaneous National Security Authorities") extends the type of information the government can obtain without a warrant to include credit card records, bank account numbers and information on Internet use.

Your checking account may tell which charities or political causes you support. Your credit card statements show where you shop, and your supermarket frequent-buyer-card records may indicate whether you keep kosher or follow an Islamic halal diet. Internet searches record your interests, down to what, exactly, you read. Faith forums or chat rooms offer a window into your thoughts and beliefs. E-mail and telephone conversations contain intimate details of your life.

A University of Illinois study found that in the 12 months following 9/11, federal agents made at least 545 visits to libraries to obtain information about patrons. This isn't just data surveillance. It's psychological surveillance.

Many Americans might approve of data mining to find terrorists. But not all of the inquiries necessarily relate to terrorism. The Patriot Act allows law enforcement officers to get "sneak and peek" warrants to search a home for any suspected crime - and to wait months or even years to tell the owner they were there. Last July, the Justice Department told the House Judiciary Committee that only 12% of the 153 "sneak and peek" warrants it received were related to terrorism investigations.

The FBI has used Patriot Act powers to break into a judge's chambers and to procure records from medical clinics. Documents obtained by the American Civil Liberties Union recently revealed that the FBI used other new powers to eavesdrop on environmental, political and religious organizations.

When Congress looks into domestic spying in the "war on terror," it should ask a series of questions:

• First, what information, exactly, is being collected? Are other programs besides the president's NSA initiative ignoring traditional warrant requirements? Are federal agencies dodging weak privacy laws by outsourcing the job to private contractors?
• Second, who has access to the data once it is collected, and what legal restrictions are set on how it can be used or shared?
• Third, who authorized data mining, and is its use restricted to identifying terrorists?
• Fourth, what is the collective effect of these programs on citizens' rights? Privacy certainly suffers, but as individuals begin to feel inhibited in what they say and do, free speech and freedom of assembly also erode.
• Fifth, how do these data collection and mining operations deal with error? As anyone who's tried to dispute an erroneous credit report can attest, once computer networks exchange data, it may be difficult to verify its accuracy or where it entered the system. Citizens who do not know they are under surveillance cannot challenge inaccurate information that may become part of their secret digital dossier.

What will Congress do to ensure that the innocent remain so?