CHICAGO — After more than a decade of warning that the greatest threat of homegrown terrorism for the United States came from individual lone-wolf radicals, the FBI and other law enforcement agencies have begun focusing on what they say is a greater threat -- small, anonymous groups of disaffected men who radicalize one another and turn to violence.
Federal officials say that most of the domestic terrorist threats now under investigation involve such groups, though they continue to rank Al Qaeda as the greatest danger globally.
Known among counter-terrorism officials as BOGs, for "bunch of guys," or GOGs, for "group of guys," the cells may offer greater opportunities for detection and infiltration than the lone-wolf threat because they are more numerous and most members are amateurs.
But they present daunting challenges as well. They are difficult to detect because most lack formal structure or prominent leaders and have little or no contact with Al Qaeda or other known terrorist organizations. They can plan multiple attacks, use varied weapons and tactics, and draw on a wider range of resources than an individual could, officials say.
More vexing still, they say, is the dynamic at work inside these groups. Most members start out as merely alienated and angry. They tend to radicalize and egg one another on with the help of the Internet, increasing the likelihood of talk turning into action. Yet it's difficult to know which of the many such groups -- some as small as two or three individuals -- might go all the way to launching an attack.
Such groups form so spontaneously and "self-radicalize" so quickly that the first sign of their existence might be an attack, Samuel J. Rascoff of the New York Police Department said at a recent counter-terrorism summit in Florence, Italy.
Rascoff, director of intelligence analysis for the NYPD, said that BOGs could "serve as an echo chamber," amplifying the influence of the most radical members.
Some defense lawyers and other critics say the threat is overblown, and often arises from law enforcement informants who entrap or even push small-time troublemakers into plotting attacks.
"There are very many cases in which the informants are the ones creating the terrorist plots," said Rocco C. Cipparone Jr., a defense attorney in one small-group case.
To illustrate the small-group threat, authorities cite the case of Derrick Shareef, a young Muslim convert. Shareef was arrested near Chicago in December on suspicion of plotting to use hand grenades to attack holiday shoppers.
Originally, authorities described Shareef as a loner. Now, they say that he was plotting with another American Muslim convert who allegedly had ties to terrorists in the United Kingdom. The two were discussing a variety of targets and tactics, including sniper attacks on U.S. troops and assaults on military recruiting stations, a federal prosecutor said at a July 28 court hearing.
The new view of Shareef resembles alleged plots against the Ft. Dix Army base in New Jersey and John F. Kennedy International Airport in New York in the spring, and Chicago's Sears Tower in June 2006, authorities say.
At the Florence conference, which was sponsored by New York University's Center on Law and Security, security officials Armando Spataro of Italy and Baltasar Garzon of Spain said their nations were seeing a sharp increase in such groups.
"It's an international phenomenon," according to one U.S. intelligence official, who said such cells were being monitored in the United States, Canada, Europe, the Middle East, North Africa and elsewhere.
"There is no useful profile to assist law enforcement or intelligence to predict who will follow this trajectory of radicalization. Rather, the individuals who take this course begin as 'unremarkable' from various walks of life," the NYPD said in a report released Wednesday.
"It is a phenomenon that occurs because the individual is looking for an identity and a cause and unfortunately, often finds them in extremist Islam," the report said.
The Council on American-Islamic Relations said the NYPD report may result in all U.S. Muslims being viewed with suspicion. The report's "sweeping generalizations and mixing of unrelated elements may serve to cast a pall of suspicion over the entire American Muslim community," Parvez Ahmed, chairman of the council's board, said in a statement.
Law enforcement officials say BOGs present unique challenges.
"If we don't bump into them directly or have someone involved in some form of interaction with them, we'll have a difficult time finding them," said Arthur M. Cummings II, the FBI's deputy assistant director for counter-terrorism.
Marc Sageman, a former CIA case officer and psychiatrist credited with articulating the "bunch of guys" concept, said when it comes to carrying out an attack, individual members "don't have the courage to do it, but collectively they do."