This month a woman killed herself and five other people in a suicide bombing in the center of Moscow. Earlier in the fall a female suicide bomber killed 21 others in a crowded Israeli restaurant. These incidents, and many others before, illustrate an important weakness in our counterterrorism strategy. The official profile of a typical terrorist -- developed by the Department of Homeland Security to scrutinize visa applicants and resident aliens -- applies only to men. That profile was developed before the advent of Islamist chat rooms recruiting operatives for a global jihad, before the war in Iraq increased anti-American sentiment worldwide and before women started serving as suicide bombers for Islamist terrorist organizations.

Under a program put in place after Sept. 11, 2001, visa applications for males between the ages of 16 and 45 are subject to special scrutiny. Women, however -- even those from countries known to harbor terrorists -- are not subjected to the program. Likewise, the requirement that resident aliens from countries such as Pakistan, Yemen and Saudi Arabia register with the federal government applies only to men.

Terrorists seek out vulnerabilities in the enemy government's countermeasures. When metal detectors were installed at airports, terrorists found other ways to attack planes. When governments began protecting their embassies with concrete barriers, terrorists turned to larger explosives. Profiling men exclusively, and also focusing so tightly on countries known to harbor terrorists, are significant loopholes that have not been closed despite the FBI's recognition that al Qaeda has begun recruiting women, and despite the discovery last spring that an MIT-trained female scientist may have been providing logistical support to al Qaeda.

Although women represent a fraction of terrorists worldwide, it is naive to assume they're not recruited to violent extremist groups. Women are responsible for approximately one-third of the suicide attacks perpetrated by the Tamil Tigers in Sri Lanka, and two-thirds of those by the Kurdistan Workers' Party. Women have founded and led terrorist groups, hijacked planes, served on all-female tank units, blown up buildings and assassinated national leaders. What is new is that women are participating in attacks on behalf of organizations that promote Islamist causes.

Islamist groups have traditionally opposed the use of female "martyrs." But in responding to the first female suicide-bombing attack in Israel in January 2002, Sheik Ahmed Yassin, spiritual leader of the Islamic Resistance Movement, or Hamas, seemed to soften this position when he said that women could participate in such attacks if there were no men available, provided they were accompanied by male chaperones. Sheik Yusuf Qaradawi, dean of Islamic studies at the University of Qatar and a leading Islamic scholar, removed even these strictures, declaring that "women's participation in the martyrdom operations . . . is one of the most praised acts of worship." A woman may "go out for jihad even without the permission of her husband," he declared, and may, if necessary, travel without male chaperones and without veils.

The dress code for devout Muslim women and norms regarding body searches could make it easier for women to hide weapons, as was the case during the French-Algerian war. Women still arouse less fear and suspicion when it comes to physical violence. As a result, they often receive less attention during searches and inspections.

The lack of scrutiny of women entering the United States and the broadly held -- and correct -- view that women are less prone to violence are likely to cause al Qaeda to turn increasingly to women and other recruits who don't fit the standard profile. According to intelligence assessments cited in the press, the al Qaeda movement is seeking recruits all over the world -- in Western prisons and inner cities, among Hispanic Americans and among French converts to Islam. Through Internet communications, it is urging individuals to create their own cells and carry out their own strikes, without necessarily joining existing militant organizations. It is also recruiting women.

Despite the legitimate concerns it raises in regard to civil liberties, profiling is appealing to bureaucracies during wartime because it allows them to develop standard operating procedures, easing the burden on those who would protect us. It may well have eased the search for terrorist suspects until now. But we are fighting an enemy that continues to change its tactics, its purported mission and the ethnicity, nationality and gender of the personnel it recruits. This means we need to rely less on these variables as indicators of potential danger.

A far more powerful instrument would be more and better human intelligence enabling us to penetrate the movement's armies, monitor its recruitment drives, predict its evolution -- including the type of personnel it will recruit -- and ultimately undermine its appeal to the broader population. In the absence of such intelligence, profiling can help, but only if those who police our borders receive regular and constant updates from the field. With such a protean enemy, to rely on standard operating procedures such as race- and gender-based profiling is to put the safety of the American people at risk.

Jessica Stern is a lecturer at Harvard's Kennedy School of Government and author of "Terror in the Name of God: Why Religious Militants Kill."