Washington — The recent report that the home of former national-security adviser Robert McFarlane might have been bugged by a government agency after he left the White House edges an old privacy issue nearer the spotlight again: surveillance of Americans. The amount of legal surveillance is modest - and known. But no one knows how much illegal tapping of phones and eavesdropping in homes and businesses occurs in the United States. Experts suspect there is a great deal.
A year and a half ago the congressional Office of Technology Assessment noted that only 392 illegal phone taps were reported to the Federal Bureau of Investigation during 1984. But the OTA concluded that far more probably took place.
Rep. Robert Kastenmeier, Wisconsin Democrat and a ranking congressional expert on surveillance, says that ``we hear reports'' of widespread illegal wiretapping.
Recent technological advances make tapping, bugging, and other types of surveillance easier and harder to detect. Listening devices are smaller and cheaper. And computers raise the specter of widespread and sophisticated monitoring, both of businesses and individuals.
In recent years privacy experts have concentrated on bringing United States laws up to date, a step achieved last November in legislation guided by Representative Kastenmeier. ``Maybe it's time'' now, he says, to put illegal tapping and eavesdropping on the agenda.
In the McFarlane case, a White House spokesman has denied that the device - designed to scramble conversations to protect privacy - which remained at the former NSC chief's home could have been used to eavesdrop. But electronic communications expert James Ross says the so-called scrambler could have been quickly and easily modified to pick up all phone conversations. The only way to tell whether a scrambler has been so modified is for an expert to examine it.
Mr. Ross is president of a private detective agency that specializes in countermeasures to surveillance. He has testified as an expert witness in several trials and is president of Communications Security Association, an international group of surveillance specialists.
Legal tapping of phone lines is done after a warrant has been approved by a state or federal court. Such surveillance is related either to criminal investigation or national security. In 1984, 801 legal taps were placed in the US for criminal reasons, the highest number since 1973, and approximately 600 for security purposes.
Well-publicized congressional hearings during the 1970s concluded that US law-enforcement and intelligence agencies conducted numerous illegal wiretaps. But no such illicit action by government agencies is apparent today. ``We just don't have any evidence'' of current illegal wiretapping by federal agencies, says Jerry Berman, legislative counsel for the American Civil Liberties Union (ACLU).
The law that Kastenmeier shepherded to passage last fall made illegal many kinds of surveillance not covered by previous statute. But experts say that in the past thousands of illegal wiretaps and buggings were undertaken despite being forbidden by law, and without the perpetrators being caught. It's too early to tell whether the new measure will put a crimp in surveillance, says Gary Marx, a sociologist at the Massachusetts Institute of Technology, who has written extensively on surveillance. ``The issue,'' he adds, ``is implementation.''
Traditionally, the largest number of illegal phone taps and surveillances were for divorce cases. Today two of the top reasons are organized crime and corporate espionage. Both depend heavily on the technical capability of tapping into information stored in computers.
``There is a pretty good likelihood,'' says Fred Wood, ``that illegal electronic activity by the criminal community is rampant.'' Mr. Wood was project director for the OTA's 1985 report on wiretaps.
Industrial espionage-by-computer is most likely in high-tech firms, he says. They are ``the ones best prepared to do electronic surveillance, and it's also where the incentives are greatest, because things change so fast.''
Woods says companies that conduct computerized espionage are seeking ``advance information on product releases, strategic planning information....''
The microchip - the basic building block of computers - made this great leap in surveillance capability possible, says MIT's Professor Marx.
To Ross, the device that is ``probably the most serious threat of all'' to Americans' privacy is a $25 transmitter, four inches square and one-quarter of one inch thick. Mass produced and for sale in many electronic stores, it is a hidden microphone that broadcasts anything said in a room through electric power lines. ``It can be put into the wall,'' he says, ``into a clock'' into anything that plugs into an electric socket.
Other small items exist: a transmitter the size of a cigarette butt, a tape recorder, small enough to fit into a pocket.
But in their possible ramifications these items are dwarfed by the opportunities that today's computers offer for monitoring the unsuspecting.
``There's the possibility,'' Ross says, ``that some of the modern computerized phone systems might be susceptible to being remotely reprogrammed'' to permit a third party to listen. ``I am quite certain that it's possible and is happening. You could reprogram a computer so that any time a certain extension dials a number, it is connected to'' someone listening in.
In a growing number of areas of the US phone companies have equipment called remobs, which is legally used to monitor the conduct of employees and the quality of phone service. In normal mode it monitors a phone line for a minute or so and then switches to another. But ``in a practical sense the equipment can be modified,'' he says, to listen to only one number.
The National Security Agency, a supersecret arm of the federal government, is capable of monitoring huge numbers of phone calls made between the US and foreign nations. These calls go through the airwaves via microwave transmissions, and NSA devices can listen to many of them.
Sources differ as to whether the agency monitors all or a large percentage of these calls. In any case a portion of some calls are actually recorded, according to ACLU's Jerry Berman. The recording is automatically triggered when callers say several key words, indicating that what they're discussing might be of security interest to the US government.
And then there is the old-time, illegal phone tap on the individual. It still occurs, Ross and others say, in sizable but unknown numbers. Unless the perpetrator is caught, which is infrequent, there's no more idea today why each of these taps was made than there ever was.