So what? We won the cold war, didn't we?
While the cold war is over, the type of espionage the Soviets practiced is still around. In fact, the Russians are still quite active in the spying business. The Communist Party is still a major force in Russia, as is a fondness, or at least tolerance, for many of the communist's police state methods. There are also several communist nations left, like China and Cuba, which still practice that very Soviet style of espionage.
The Soviets didn't really invent anything new in the spying business, but they energetically improved upon ancient techniques and thus made the 20th century a golden age for espionage. Basically, the Russians realized that successful spying was all about developing a lot of personal relationships, and then exploiting as many as possible. Early on, in the 1920s and 30s, the Soviets had a lot of capable and eager agents. And there were many communist sympathizers worldwide. Thousands of these pro-communists were turned into valuable Soviet agents. Those that got caught were declared "martyrs." Nothing was wasted.
Stalin's purges in the late 1930s brought this golden age to an end. Most of the excellent agents were executed. Many of the spies began to have second thoughts about working for the Soviet Union. But then World War II came along and made recruiting spies easier for a time. This continued for a while after World War II. But without the large number of skilled agents, some new enticements were used. The most frequently used ploy was to threaten the safety of relatives behind the Iron Curtain. Western counterintelligence soon caught on to this, and having relatives back in the old country kept a lot of people from getting security clearances or sensitive jobs. But the Soviets had many more techniques they could use. Sex and blackmail (often used together) were very successful. Attractive men and women were recruited, trained and sent forth to be romantic for the revolution. This worked particularly well in West Germany, where East German spy studs recruited a number of key female staff in NATO and West German organizations. But this pointed up another problem the Soviets were having, the collapse of communist idealism and Stalin's purges had eliminated (except in Germany) a supply of agents who could "pass" for foreigners on their home ground. America was particularly difficult, with it's multiplicity of customs and odd accents.
By the 1970s, the Soviets were reduced to using the most basic of all offers; money. This worked quite well, and until the end of the cold war, Western nations refused to realize how successful this approach could be. We also underestimated how many secrets could be uncovered by simply collecting all the information freely available in a democracy. In the last two decades of the Soviet Union, it's spies were increasingly successful in obtaining valuable information this way, but telling their bosses it was really from well placed spies. The spymasters in the Kremlin never caught on to this little deception, and didn't care as long as the good stuff kept coming back to Moscow.
Other nations have developed new angles that are, in come ways, superior to the Soviet techniques. China, for example, has had large overseas populations for centuries. These "overseas Chinese" usually did not assimilate and retained considerable loyalty, and family connections, with the homeland. For many decades after World War II, most overseas Chinese were either anti-communist or reluctant to get involved with Chinese politics. But once China began economic reforms in the 1970s, this changed. It was OK to visit China, and to receive Chinese officials in America. This was China's espionage opportunity. While the Russians had few agents who could pass for Americans, and operate freely in the U.S., China's spies could get away with just being Chinese. They used the soft sell, realizing that by collecting small bits of information from many people who did not even consider themselves spies, they would be very difficult to stop. From time to time, the Chinese received large, and obviously illegal, amounts of information. But the most important aspect of this technique is that it is difficult to stop, and you don't even have many indictable spies to catch. Picking up small pieces of information from many sources is an ancient technique. The Chinese also make good use of the old Soviet "open source" opportunities. But combining this with the many minor bits of data gleaned from unsuspecting overseas Chinese scientists and engineers provided a constant supply of useful foreign secrets.
Other nations, like Iraq and Iran, have also used the Chinese approach. Both nations have a large number of scientists and engineers living and working overseas. Many of these people are recent immigrants to America and Western Europe. If someone shows up from the old country, with a plausible story and a desire to talk shop, well, what's a homesick engineer to do? Call the FBI?
Foreign spies also know that Americans have short memories and a distaste for spy hunts. But the spies are out there, and a little practical paranoia is in order.
Practical Paranoia; Back in the 1980s, there was a movie, "Red Dawn" that showed American guerillas resisting a fictional Soviet invasion via Nicaragua and Mexico. The critics dismissed the flick as "racist: and totally unbelievable". Subsequent revelations from Moscow archives revealed that the Soviets did have a plan to move saboteurs, from Nicaragua, across the Mexican border, disguised as illegal aliens. Radar stations, pipelines and power towers were all targeted in great detail, as were port facilities in places like New York City. The Soviet archives opened enough in the early 1990s (when a fist full of hundred dollar bills could work wonders) to a create a flurry of well documented proofs. The Rosenbergs were Russian spies, Alger Hiss was mixed up in communist espionage and the American Communist Party was in the pay of the Soviet Union and served as a tool for espionage and subversion. Many left wing writers and politicians were either on the Soviet payroll, or eager to assist Soviet espionage activities.