The arrest on a morals charge last June of a 44-year-old Briton named Geoffrey Arthur Prime has precipitated another major spy scandal, prompting the inevitable deluge of questions about the security of Western intelligence services. The resultant speculation tends to obscure the fundamental questions that the Prime case raises about how a free society protects itself in this strife-ridden era of potential thermonuclear war. Prime, subsequently charged under Section 1 of Great Britain's Official Secrets Act, was from 1968 to 1977 a Russian linguist and translator for the General Communications Headquarters. GCHQ is the British analogue to the United States' National Security Agency, and the two are among the most important intelligence organizations in the Western alliance. It appears that during this entire period, Prime had been working with and for the KGB.

Presumably Prime worked on Russian documents, translating them into English. If so, he certainly could have given his KGB case officers detailed information about -- probably copies of -- all the documents he worked on. This, at a minimum, would have given the KGB a catalogue of specific, sensitive Soviet documents or communications demonstrably compromised. From that catalogue, the KGB might have been able to ascertain the collection methods through which many of those documents probably came into allied hands--knowledge that would have enabled the Soviets to crimp the flow of important intelligence to NATO or perhaps (in some cases) to play disinformation games.

All major intelligence services pay careful attention to basic principles of "compartmentation" and "need-to-know," two matters on which the British have long been stricter than most, particularly in the communications field. Hence, it is most unlikely that Prime would have been apprised of precisely how the documents that flowed across his desk for translation were acquired.

It is equally unlikely that his official duties would have given him any appreciable access to NATO communications, other than those quoted in Russian texts, or "positive" NATO-related information, such as the location of nuclear weapons or the current disposition and readiness status of NATO military units.

Prime apparently was first recruited by the Soviets in the early 1960s, when he was a Royal Air Force sergeant stationed in West Berlin. As I know from experience, this would have been perfectly in keeping with Soviet practice.

If anyone in Germany, of any nationality, who is or might be useful to Soviet intelligence shows any sign of vulnerability or develops a personal problem -- financial, family, sexual or whatever -- he or she is quite likely to get a probing Soviet or Soviet-sponsored approach, a visit designed to appear fortuitous and totally innocent. The Soviets and their surrogates frequently play for the long haul, picking up potential recruits whose immediate usefulness poses might be slight, but who can be guided or maneuvered -- over years, even decades -- into positions of progressively greater sensitivity and value.

It is not easy for open Western democracies, whose legal codes mandate a presumption of innocence, to counter such Soviet efforts. These governments must continually strike delicate, politically charged balances between the requirements of security and the imperatives of the legal, moral and political traditions these governments are required by their electorates to uphold.

For a variety of cultural reasons, including concern for privacy, our British allies have long been reluctant to pursue the kind of thorough background investigations ("positive vetting") that are routine in the United States for anyone seeking government employment, especially for positions involving access to classified information. In particular, the British are far less prone than we are to use the polygraph test extensively and routinely in such situations.

As a general rule, it would be extremely difficult for Americans in continuous, witting contact with the KGB to undergo the periodic polygraph examinations routine in the United States for those in positions such as Prime held, for nine years, without causing an alarm to be raised.

Heaving stones across the Atlantic on such matters is liable to break a good deal of American glass. In the United States, it has long been fashionable to be more than a trifle sanctimonious about Messrs. Philby, Burgess, Maclean, Blunt and other people of that ilk who represented security disasters -- forgetting our Boyce, Lee, Martin, Mitchell, Kampiles and Agee. It was not really old school ties, an "old-boy" network or a class structure, however, that protected the likes of Kim Philby before and after World War II. It was a set of powerful attitudes and emotions that exist, with equal strength, on our side of the Atlantic.

To many Britons in the 1930s through the 1950s, the notion that someone like Kim Philby might be a Soviet agent was almost literally unthinkable. As a result, certain groups or classes were effectively put "off limits" for security concerns, let alone systematic investigation. Smart Soviet intelligence officers naturally would -- and clearly did -- devote special attention to the screening and cultivation of young intellectuals with the "right" sort of upper-class educational and family backgrounds.

In the America of the 1980s, for similar reasons, sophisticated Soviet recruiters would focus on elements afforded the kind of social protection that educational and family background afforded certain Britons a half century ago.

In this light, an idealistic, minority, female, staff member of a key congressional committee, for example, would be an ideal candidate. And anyone who ever raised security-related questions about her would be charged immediately with, among other things, racism, sexism, contempt for Congress and "McCarthyism." Consider the furor Sen. Jeremiah Denton engendered by suggesting that some in the nuclear freeze movement might have objectives a bit less altruistic and noble than a pure, disinterested quest for world peace.

The Prime case is a graphic reminder that we live in a difficult and dangerous world. It underlines the thorny questions with which free governments must continuously wrestle -- how to preserve their freedom, and that of their allies, from external aggression without abandoning the internal values that make them free.