Terrorist groups get around post-Sept. 11 restrictions on banks and charities by turning to couriers to smuggle cash across borders to finance terrorism plots, a trend that U.S. intelligence has seen increasing in the past year. Intelligence gathered from captured terrorist suspects and other sources indicates "a trend toward bulk-cash smuggling and use of cash couriers," Stuart Levey, undersecretary of Treasury for terrorism and financial intelligence, told USA TODAY. Reliance on cash makes it harder for terrorist groups to raise money from wealthy individuals or charities accustomed — until their activity drew the attention of Treasury enforcement — to conveying money through the banking system, Levey said. Cash also makes distribution to front-line terrorist cells plotting attacks more cumbersome. Terrorist groups have had to break up cash into smaller amounts to keep one weak link from crippling a terrorism operation, he said. "It's a lot less efficient," Levey said. "Some cash couriers get caught. Some get greedy."But cash is difficult for law enforcement to track, Levey said. International efforts to block illegal cash smuggling have been slow in coming, particularly in the Middle East, where there is a tradition of carrying large sums. Compared with conventional military operations, terrorist attacks are relatively inexpensive. Modest sums can finance damaging attacks.