It is called Sluzba Bezpieczenstwa. And the fact that most Americans don't know what it is - let alone how to pronounce it - goes a long way in explaining why the Polish intelligence organization, SB, has been so successful in obtaining sensitive details of this country's most secret defense systems.
It is said to rank second only to the Soviet KGB in terms of spying activity in the United States. And - like the KGB, with which the SB is linked - the primary target is technology, particularly US military technology.
''Polish intelligence is actively targeting US classified information and technology. The threat is serious in this country,'' says Phillip A. Parker, deputy assistant director of the FBI's Intelligence Division.
The SB's record speaks for itself. According to two spy cases involving Poland which have been made public in recent years, the organization has acquired:
* Volumes of classified information on American efforts to design a system that would enable US Minuteman nuclear missiles to survive a preemptive nuclear attack by the Soviet Union.
* Plans for the ''quiet'' radar system for the B-1 and Stealth bombers.
* Details of the ''look-down, shoot-down'' radar system for F-15 fighters.
* An all-weather radar system for US tanks.
* Information on the Phoenix air-to-air missile used on Navy F-14 fighters.
* Documents on the Patriot surface-to-air missile.
* Details of the improved Hawk surface-to-air missile.
The method used by the SB to obtain these military secrets was a simple one: They bought them for cash from American citizens, often at bargain-basement prices.
The Minuteman missile documents cited above were sold to Polish agents in 1980 and '81 by an American engineer who received $250,000, according to the FBI. The documents were considered so important in Poland and the Soviet Union that the Polish agents received two commendations for their efforts, one of them signed by the man who was then chief of the KGB, Yuri Andropov.
The American engineer who reportedly sold the documents, James D. Harper Jr., was indicted in early December by a San Francisco grand jury on six counts of espionage and three counts of tax evasion. He denies the charges.
All the other documents cited above were sold to Polish agents between 1978 and '81 by an American engineer at Hughes Aircraft Company. The engineer, William H. Bell, received payments of $110,000, according to the FBI.
Mr. Bell is serving an eight-year prison sentence in California. Marian Zacharski, the man who recruited Bell for the Polish intelligence service, was sentenced to life in prison for his part in the espionage scheme.
Though the Bell case went to trial in 1981 and the Harper case is not expected to go to trial until midyear, both Harper's and Bell's involvement with Polish agents took place during roughly the same period of time in the late 1970 s.
The two cases offer a rare glimpse into the workings of the Polish intelligence organization and the murky world of Soviet-bloc espionage in the US.
According to an FBI affidavit filed in the Harper case, the Polish intelligence organization is divided into units or ''wydzials,'' each with an individual KGB liaison officer.
The affidavit says that each year, Soviet officials in Moscow compile a master ''shopping list'' of desired Western technology and research. The master list is broken down into sublists and delivered to allied Warsaw Pact intelligence services.
One such sublist is delivered to Polish intelligence officials in Warsaw. The Poles subsequently break that list down even further. The resulting sublists are delivered to agents or other sources based on their areas of expertise and ability to acquire items on the list.
It was at this level that James D. Harper Jr. was operating in 1979, according to the affidavit. The affidavit quotes Harper as saying that he would further break down his list ''as a function of my contacts in government, private industry, (and) free lancers to yet another sublist.''
Harper was working primarily in the area southeast of San Francisco known as Silicon Valley where an estimated 700 companies are in competition at the cutting edge of the high-technology research industry. Many of the companies vie for classified military research and development projects such as designing and constructing components of missile guidance systems and high-speed integrated circuits that are used in sophisticated jet fighters and cruise missiles.
Competition among the companies has grown to such proportions that intercompany spying is commonplace, according to businessmen and law enforcement officials. In addition, the region is said to be a center for a wide range of foreign espionage efforts.
This is the environment in which Harper worked.
According to court documents, Harper - who had no security clearance - used his contacts in Silicon Valley and, apparently, even his wife to gain access to desired classified documents.
Harper's wife, who died last summer after a long illness, was a secretary and bookkeeper at Systems Control Inc. (SCI) in Palo Alto, Calif. She had a security clearance as well as access to documents pertaining to the Minuteman missile project, according to the FBI.
In examining documents at SCI, federal agents found 118 of Harper's fingerprints on 11 different documents - all of them marked either ''secret'' or ''classified.'' Next: SB's intelligence bonanza