Soviet intelligence has generally been known for its excellent ability to recruit human sources (Humint), however, during the later stages of the Cold War these Humint capabilities went into sharp decline before having some success again during the final years of the Cold War.

The 1968 invasion of Czechoslovakia had a deeply demoralizing impact on Soviet intelligence, as it undermined faith in the moral superiority of the Socialist system, but also shattered any hopes of finding Communist sympathizing would-be spies in the West like they did in the 1930's and 1940's that resulted in the USSR's most famous intelligence victories. The combination of ideological and economic stagnation back in the USSR also fuelled corruption among the Soviet officialdom with access to Western luxury goods, and further caused an increase in the number of KGB and GRU officers defecting.

During the mid 1970's, Vladimir Kryuchkov was appointed as chief of the PGU (KGB Foreign Department), who had no official training in intelligence matters but got his job because he had been a loyal personal secretary to KGB Chairman Andropov. Naturally, his lack of experience and rather dogmatic ideological views made him deeply unpopular among the staff. Kryuchkov began to urge KGB residencies across the globe to step up their efforts to recruit new agents and demand more results. Like a typical Soviet apparatchik, Kryuchkov believed he could raise the KGB's productive output by merely increasing the quota's. The result was that intelligence officers began to report every casual talk to a Westerner as an agent recruitment while cabling Moscow little more then summaries of Western newspaper articles.

The East-German intelligence service HVA was even asked to provide training to the KGB on the art of setting up ''illegal'' agent networks, a method the KGB had still mastered during the golden days of the 1930's, but had lost.

During the final decade of the Cold War, the Soviets began to modernize their operations somewhat and enjoyed some considerable successes. Computer analyses were used in 1979 to predict the outcome of the Cold War, and these produced a bleak picture. As a result, and also due to the growing international tensions, a massive nuclear early-warning program called RYaN was set up, involving both the KGB and GRU and all intelligence services of the Warsaw Pact. They collected massive volumes of data on NATO political and military developments in order to be able to timely predict a Western surprise attack. To process all this data, the KGB set up a new analysis department in 1983, which remained very small compared to the analysis component of the CIA. Intelligence analysis had never played a large role in Soviet intelligence, but it was getting more important. Much of the raw intelligence collected for the RYaN program however was through satellite services of East-Germany and Hungary with better access to NATO documents.

During the 1980's, the Soviets also benefitted from some notorious cases of Americans offering to spy, within the NSA, FBI, CIA and the US Army. With the help of these, the USSR acquired detailed NATO war plans and managed to destroy the CIA's agent networks inside the USSR, including its most valued asset - Dimitry Polyakov, a GRU officer who had been spying for more than 20 years.

Under Gorbachev the focus of Soviet intelligence shifted increasingly towards technological, scientific and industrial espionage. Project RYaN lost its importance as the nuclear threat was diminished. By 1989 for example, 40% of the East-German HVA staff worked in scientific espionage, the results of which were shared with Moscow. Aside from industrial espionage, Gorbachev tended to ignore KGB reports as they were full of ideological clichés and anti-Western conspiracy theories of the kind that Kryuchkov demanded from his staff, while Gorbachev instead wanted to cooperate with the West. The KGB failed to adapt to what he called ''New Thinking''.

I hope this answers your question a bit.

For further reading I can highly recommend:

Comrade Kryuchkov’s Instructions: Top Secret Files on KGB Foreign Operations, 1975-1985 (Stanford 1993), Christopher Andrew and Oleg Gordievsky

Near and Distant Neighbours: A New History of Soviet Intelligence (Oxford 2015), Jonathan Haslam

Soviet Leaders and Intelligence: Assessing the American Adversary During the Cold War (Washington DC 2015), Raymond L. Garthoff

Spy Handler; Memoir of a KGB Officer (New York 2005), Victor Cherkashin

Spymaster; My Thirty-two Years in Intelligence and Espionage against the West (Philadelphia 2009), Oleg Kalugin

The Sword and the Shield: the Mitrokhin Archive and the Secret History of the KGB (1999), Christopher Andrew & Vasili Mitrokhin