Officials say a small network of "entrepreneurs" is responsible for the bulk of the illicit trade in arms and high-technology items.

"It's like any network, perhaps a little less accessible and less formal but, if you're interested, you can find out who to go to," said a State Department official familiar with the problem.

"There is a well-known core group," said Roger Urbanski, director of the Customs Service Strategic Investigations Division. Customs, as part of a program dubbed "Project Snare," has established a "Ten Most Wanted" list of suspected arms brokers.

Customs Commissioner William von Raab made the list available to The Washington Post. The individuals, believed to be operating abroad, are:

*Richard Mueller, a West German charged in the largest Soviet diversion discovered by the United States, involving sophisticated computer equipment that would have greatly advanced Soviet capabilities to manufacture military-grade semiconducters.

*Otto Hermanus von Olst, a suspected Dutch munitions dealer operating worldwide.

*Cyrus Hashemi, a suspected Iranian munitions dealer, and fugitive from charges of conspiring to export military and stragetic equipment to Iran in 1980 and 1981.

*Charles McVey, a suspected American high-technology merchant, and fugitive from charges of unlicensed export of state-of-the-art computers and related equipment.

*Fred Schiavo, a suspected Swiss high-technology merchant accused of conspiring to export $1 million worth of computers to the Soviet Union through Canada.

*Dieter Enderlein, a Swiss national accused with Schiavo in the computer export conspiracy.

*Bryan Williamson, a British national indicted on charges of arranging illegal export of computers to Bulgaria via West Germany.

*Col. Najmeddin A. El-Yugi, a Libyan procurement official accused in the largest illegal export case in U.S. history, involving a conspiracy by a Chicago company, TENCOM Inc., to export $14 million worth of C130 aircraft parts and helicopter parts to Libya through West Germany and Italy.

*Dietmar Ulrichshofer, an Austrian fugitive from charges of unlicensed export of computers, electronic and communications equipment worth $10 million to the Soviet Union.

*Allen Simmonds, an Englishman suspected of diverting high-technology equipment.

The man who had headed the list, West German Werner J. Bruchhausen, a fugitive from a 1981 indictment charging him with conspiring to smuggle semiconductor technology to the Soviet Union, was arrested in May by British authorities.