WASHINGTON — In the early 1990s, Osama bin Laden worked out of an ordinary eight-room building on McNimr Street in downtown Khartoum, Sudan. His office was the first one on the left, behind the receptionist. Like bosses everywhere, Mr. bin Laden had trouble keeping his computers up. When he was feeling generous, he parceled out bonuses of sugar, tea, and oil.
In short, it was an office like any other - except that sometimes faxes and files dealt with secret weapon buys, as well as legitimate deals.
Bin Laden left Sudan long ago, and is now the most wanted man in the world. But the image of his terrorist network as an entrepreneurial conglomerate remains an accurate one, according to US officials.
What's one way to track such a net? Follow the money.
President Bush's Tuesday order freezing assets of suspected Islamic terrorist groups and individuals won't close off all bin Laden's funds, of course. In many instances, the trail of a credit-card receipt or bank account linked to terrorism is impossible to follow to its end.
Nor are there untold millions to follow. If anything, bin Laden's organization is remarkable for how little cash it has needed.
But the order could make it more difficult for bin Laden associates to operate, while increasing the pressure on countries that shield terror networks, and building links to allies in the fight against the modern era's faceless foe.
Freezing assets "helps remind people that our strategy against terrorism doesn't have to be ... solely military," says Jim Walsh, a political scientist at Harvard University's Kennedy School of Government.
As the US tries to increase the financial pressure on bin Laden, it is important to remember that his group is more than a band of fanatics who call Afghani huts home. According to testimony presented in the recent New York trial of suspects in the 1998 bombing of US embassies in Kenya and Tanzania, bin Laden's Al Qaeda is an odd, partly self-financing, medium-size operation.
That leaves investigators numerous openings and potential points of financial leverage. "Coordinating and maintaining a group of this size takes money," says Professor Walsh. "This is thousands of people we're talking about here."
The government's first witness in the recent embassy terror trial, Jamal Ahmed Al-Fadl, a self-described former Al Qaeda paymaster, painted a vivid and detailed picture of bin Laden's financial scope.
Among the legitimate businesses Al Qaeda used to generate funds were Ladin International, an export-import firm. Taba Investments was the conglomerate's currency trading group. Hura Construction built roads and bridges in Sudan.
An agricultural holding company dealt in peanut farming, corn, and sunflowers.
Not all these efforts were successful. The farms, in particular, were problematic. But they helped provide cash infusions to Al Qaeda cells. Ex-paymaster Al-Fadl described carrying $100,000, in $100 bills, on a courier mission to Jordan.
The organization also derived cash from wealthy donors and charitable groups associated with radical Islamists.
Such self-described charities are among the targets of Mr. Bush's executive order.
Specifically, the order froze assets linked to bin Laden himself, and 26 other people and groups suspected of helping him. It also threatened financial retribution against foreign banks that do not cooperate in the US money trail effort.
Not that tracking bin Laden's assets will be easy. Using records left behind by suspects in the Sept. 11 attacks, US investigators may well be able to track bank accounts and financial transfers - up to a point. If a trail leads to Afghanistan, or some other nation suspected of supporting terror, it will end there. If the suspects made extensive use of the Islamic hawala system of moving money, which entails unregulated transfers of cash made with minimal records, it could be difficult to backtrack their dealings.
Many of the terrorists from last week's strikes made extensive use of debit cards, notes Larry Crumbley, a Louisiana State University professor and expert in investigative accounting. "If those cards were set up by cash brought into the country, it would be largely untraceable," he says.
Other experts note that Bush's order goes only somewhat further than similar efforts launched in the Clinton years.
But the order allows the US to go to some nations known for financial secrecy, such as Switzerland, and ask for help. Retaliation against any banks that refuse to cooperate would be a notable step in the effort to dry up any remaining national support for terror groups.
"You are trying to get at the hidden part of the iceberg, because if you can get it, the top part can't float anymore," says Jonathan Winer, a former US deputy assistant secretary of State for international law enforcement.