The Biggest Cases of Espionage in American History

Being the world’s most powerful country today, the United States of America is considered to have the best and the most sophisticated intelligence and national defense systems. The Central Intelligence Agency (CIA) and the Federal Bureau of Investigation (FBI) engage in coordinated efforts to effectively identify, capture, and penalize enemy agents responsible for endangering national security.

The United States has safeguarded its secrets against internal spies since the American Revolution in the 1770s. Nevertheless, there have been traitors who devoted their time to giving away important and highly sensitive data to foreign governments or organizations in exchange for financial gain or supporting their ideological beliefs. CEOWORLD Magazine published this article which features the Biggest Cases of Espionage in American History. The publication’s researchers reviewed information on espionage cases committed by American nationals from the United States Department of Defense’s Defense Personnel and Security Research Center.

In CEOWORLD Magazine’s list, readers will discover that the secret agents are American and foreign-born criminals who put the United States’ people at risk. The spies were also determined women and men who operated alone or in groups. Some of these enemy agents banded together with their colleagues, spouses, children, and friends.

Common espionage motivation is financial gain. Many of the worst offenders’ motive for perpetrating the crime was money, despite most of them earning less than US$10,000 for their illicit activities, based on the information that the United States Department of Defense gathered. Ideology is another reason why many secret agents became turncoats. Meanwhile, other spies felt intrigued or pure boredom, resulting in their espionage activities.

The following are the 25 notorious spies ranked from the longest to the shortest time they committed their espionage acts:

1. Larry Wu-Tai Chin
   a. Number of years conducting espionage: 33
   b. Beginning date of espionage: 1952
   c. Date of capture: November 22, 1985
   d. Country or organization spied for: China
   In CEOWORLD Magazine’s “25 Notorious Spies in American National Security History” list, Larry Wu-Tai Chin tops the roster. He was a CIA employee who perpetrated espionage for 33 years. This Chinese-born linguist spied for his country of origin for over three decades. Chin’s espionage activities resulted in considerable data leakage about the US Government’s policies and strategies, specifically those related to China. Chin was convicted for his spying acts. However, he took his own life in his prison cell in 1986 prior to his sentencing.
2. George Trofimoff
   a. Number of years conducting espionage: 31
   b. Beginning date of espionage: 1969
   c. Date of capture: June 14, 2000
   d. Country or organization spied for: Union of Soviet Socialist Republics (USSR) or the Soviet Union
   In 2001, George Trofimoff was proven guilty of espionage for the Union of Soviet Socialist Republics or the Soviet Union throughout much of the Cold War. Decades before that time, he worked as a US Army Reserve colonel and as a civilian in the US Army’s intelligence unit in Germany. In the 1970s and 1980s, Trofimoff sent secret documents to the Komitet Gosudarstvennoy Bezopasnosti or KGB, the USSR’s primary security agency. Money was his motivation for his illegal activities, and his life sentence made him the highest-ranking US military official to ever be convicted of spy crimes.
3. Robert Stephan Lipka
   a. Number of years conducting espionage: 30 years, 6 months
   b. Beginning date of espionage: September 1965
   c. Date of capture: February 23, 1996
   d. Country or organization spied for: USSR or the Soviet Union
   Robert Stephan Lipka made it on CEOWORLD Magazine’s roster of the 25 most damaging spies in US national security history for doing illicit work for more than three decades. This American national served as a National Security Agency clerk between 1964 and 1967. Lipka betrayed his employer. Instead of destroying classified documents, he kept many of them. At the Soviet Union’s embassy in Washington, D.C., the secret agent offered to submit a vast array of confidential information for money. In February 1996, the US Government detected Lipka’s espionage. He was captured and consequently sentenced to an 18-year jail time.
4. Walter Kendall Myers
   a. Number of years conducting espionage: 29
   b. Beginning date of espionage: 1980
   c. Date of capture: June 4, 2009
   d. Country or organization spied for: Cuba
   Walter Kendall Myers worked as a US State Department official. For almost thirty years, he conspired with his wife, Gwendolyn. Together they gave away highly classified data to the Cuban Intelligence Service. Myers’s codename was “Agent 202” and, in 2010, he received a life sentence and is ineligible for parole. This enemy spy was considered specifically harmful to US interests because of the breadth and depth of the sensitive data he leaked.
5. Carlos Alvarez
   a. Number of years conducting espionage: 29
   b. Beginning date of espionage: 1977
   c. Date of capture: January 9, 2006
   d. Country or organization spied for: Cuba
   Carlos Alvarez is another spy criminal in CEOWORLD Magazine’s list who connived with his wife, Elsa, in conducting espionage acts for the Cuban government. The former Florida International University professor and his spouse transmitted classified information relating to US military, economic, and political affairs. Alvarez and his wife were captured in 2006 for their nearly three-decade criminal operations. They pleaded guilty to the spying charges and their case marked a watershed moment in US-Cuba relations’ history.
6. Norman John Rees
   a. Number of years conducting espionage: 29
   b. Beginning date of espionage: 1942
   c. Date of capture: 1971
   d. Country or organization spied for: USSR or the Soviet Union
   Italian-American oil engineer Norman John Rees became a secret agent for the USSR after developing Communist sympathies before World War II. In 1942, he started giving away sensitive oil-related information to the Soviet Union. The FBI hired Rees in 1971 to work as a double agent. One analyst cited that this event happened following the American spy transforming into the most significant person in the Russian oil sector’s development from 1945 to 1960. Rees was dispatched to conduct espionage on his Russian government contacts.
7. Ben-Ami Kadish
   a. Number of years conducting espionage: 28 years, 11 months
   b. Beginning date of espionage: June 5, 1979
   c. Date of capture: April 22, 2008
   d. Country or organization spied for: Israel
   Ben-Ami Kadish was an American mechanical engineer who served at the US Army’s Picatinny Arsenal in New Jersey. Federal prosecutors accused Kadish of providing sensitive military information to Israel.
   The details were about an F-15 fighter jet’s altered edition and nuclear armaments. In 2008, Kadish was captured for spy-related acts. He confessed to his espionage activities the following year and pleaded guilty.
   Nevertheless, he did not receive a prison sentence and was instead fined US$50,000. Kadish’s spying case is considered notable for emphasizing the problem of allies like the United States and Israel spying against each other.
8. Dongfan Chung
   a. Number of years conducting espionage: 27
   b. Beginning date of espionage: 1979
   c. Date of capture: September 11, 2006
   d. Country or organization spied for: China
   Dongfan Chung was a Chinese-born American spy who held a confidential security clearance via his work in companies Boeing and Rockwell. He employed his position in disseminating classified data to China. The information related to the Delta IV rocket and US space shuttle programs. In 2010, Chung was convicted for economic espionage. His 16-year prison sentence is the first-ever judgment under the 1996 US Economic Espionage Act, a federal law criminalizing trade secrets misappropriation and theft.
9. Kurt Allen Stand
   a. Number of years conducting espionage: 25
   b. Beginning date of espionage: 1972
   c. Date of capture: October 4, 1997
   d. Country or organization spied for: East Germany
   For 25 years, Kurt Allen Stand spied for East Germany with his wife, Therese Marie Squillacote, and friend James Clark (see number 12). He was a member of the Communist Party of the United States of America and was a former union activist. Stand was a recruiter, bringing Clark into his espionage operation. He also served as a courier, passing secret details to his handlers. Stand performed spying activities for financial gain. He was sentenced to 17 years and six months in federal prison.
10. Chi Mak
    a. Number of years conducting espionage: 22
    b. Beginning date of espionage: 1983
    c. Date of capture: October 28, 2005
    d. Country or organization spied for: China
    Chi Mak was an American engineer. He was born in China and worked in a California-based firm, Power Paragon. Today, this former L-3 Technology subsidiary is L3 Power Paragon, a worldwide leader in the manufacture, development, integration, and engineering of power conversion and distribution systems. The offerings of Mak’s employer are for advanced industrial, governmental, and defense applications. The enemy spy’s work at Power Paragon involved himself illegally passing classified naval technology-related data to the Chinese government for more than 20 years. Mak’s spying operations were a component of a broader Chinese espionage campaign to get foreign information and technologies. In 2007, the secret agent was convicted for conniving to export American defense technologies to China.
11. Robert Philip Hanssen
    a. Number of years conducting espionage: 22
    b. Beginning date of espionage: 1979
    c. Date of capture: February 18, 2001
    d. Country or organization spied for: USSR or the Soviet Union
    Robert Philip Hanssen worked as an FBI agent. In 2001, he was captured for spying activities spanning more than two decades. Hanssen served as a double agent for the USSR, which is now Russia. His long tenure as a secret agent is deemed among the most damaging espionage cases in American history. Between 1979 and 2001, Hanssen sold vast amounts of US classified information to Russia. This secret agent was reportedly drawn by the tradecraft’s theatricality. He reportedly wore black turtlenecks reminiscent of Cold War spies’ “golden age.” Hanssen reportedly performed this act in doing dead drops with his handler in his Washington D.C. suburban residence. This spy’s illicit activities resulted in the execution and exposure of several American secret agents. They also compromised many US operations, severely damaging the country’s intelligence.
12. James Clark
    a. Number of years conducting espionage: 21
    b. Beginning date of espionage: 1976
    c. Date of capture: October 4, 1997
    d. Country or organization spied for: East Germany
    James Clark was a University of Wisconsin student when he developed Communist sentiments. In 1976, a leftist campus group hired him to become a spy, per a report from his conviction date. Clark gained security clearance via his defense contractor job. He obtained access to more documents from the US State Department workers. Clark felt inspired to give away sensitive files to East Germany for at least a decade. In 1998, he was convicted of conspiracy to perpetrate espionage. Clark received a jail sentence of 12 years and seven months.
13. Ana Belen Montes
    a. Number of years conducting espionage: 21
    b. Beginning date of espionage: 1980
    c. Date of capture: September 21, 2001
    d. Country or organization spied for: Cuba
    Ana Belen Montes worked as a US Defense Intelligence Agency senior analyst. For more than two decades, she gave away confidential details to the Cuban Intelligence Directorate. The information consisted of unraveling four American secret agents and disclosing US military exercises. Montes was convicted of espionage and served a 25-year jail sentence.
14. Ronald N. Montaperto
    a. Number of years conducting espionage: 21
    b. Beginning date of espionage: 1983
    c. Date of capture: February 4, 2004
    d. Country or organization spied for: China
    Ronald Montaperto worked as a US defense analyst. The FBI underwent several stalled probes. However, the agency successfully outsmarted Montaperto in a polygraph test for a faux employment interview. The secret agent admitted to giving away many top-secret details to Chinese military attachés. In 2006, Montaperto was found guilty of disseminating sensitive data to China. His espionage acts are believed to have partly led to the Asian economic giant successfully avoiding a US eavesdropping activity that monitored its ties to illegal armament sales, per US officials.
15. Amen Ahmed Ali
    a. Number of years conducting espionage: 19
    b. Beginning date of espionage: 1987
    c. Date of capture: September 7, 2006
    d. Country or organization spied for: Yemen
    Amen Ahmed Ali served as a Yemeni spy for almost 20 years. He was proven to have conspired to export pilfered files and unlicensed US military equipment to Yemen. Such materials included night vision goggles, bulletproof vests, and chemical protective suits. Ali admitted that he had served as an unlawful secret agent on behalf of the Republic of Yemen’s Armed Forces Department since 1987. He remarked on these details in a plea agreement he entered many years later. Ali was captured in Bakersfield, California. His arrest is the outcome of a long-term probe by local police departments and the FBI.
16. John Anthony Walker, Jr.
    a. Number of years conducting espionage: 17 years and 5 months
    b. Beginning date of espionage: January 1968
    c. Date of capture: May 20, 1985
    d. Country or organization spied for: USSR or the Soviet Union
    John Anthony Walker, Jr. is among the enemy spies included in CEOWORLD Magazine’s “25 Notorious Spies in American National Security History” list. This former US Navy officer gave away secret military data to the USSR in exchange for money. Walker’s spying operations involved an espionage ring that included his son, Michael, and his brother. His ex-wife informed the law enforcement authorities regarding his illegal activities but was unaware that their son was also involved. Walker and his cohorts were captured, charged, and sentenced to life imprisonment. Nonetheless, his son received a 25-year jail sentence. In 2014, Walker passed away in jail, which was one year prior to his being eligible for parole. This infamous spy’s forbidden acts severely harmed US national security during the Cold War. After all, USSR spies successfully decrypted more than one million concealed naval messages. They also tremendously developed their naval warfare capacities, thanks to Walker’s betrayal of the US Government.
17. Clyde Lee Conrad
    a. Number of years conducting espionage: 14
    b. Beginning date of espionage: 1974
    c. Date of capture: August 23, 1988
    d. Country or organization spied for: Hungary and Czechoslovakia
    Clyde Lee Conrad served as a US Army non-commissioned officer. From 1974 to 1988, he allegedly sold the confidential documents and defense agendas of the North Atlantic Treaty Organization (NATO) to Czechoslovakian and Hungarian intelligence bureaus. Conrad’s spying activities damaged the NATO and US military operations during the Cold War. In 1988, West German authorities arrested this secret agent who was tried and found guilty in Koblenz, West Germany. Conrad paid more than US$1 million as a fine and was sentenced to life imprisonment. In 1998, he passed away in prison at the age of 50 due to a heart attack.
18. Katrina M. Leung
    a. Number of years conducting espionage: 13
    b. Beginning date of espionage: April 1990
    c. Date of capture: April 9, 2003
    d. Country or organization spied for: China
    Katrina Leung served as a Chinese-American entrepreneur. In the 1980s, the FBI hired her to get intelligence on China. In the early 2000s, Leung’s case was discovered and is considered one of the most devastating espionage scandals in US history. Leung was found to have been furtively transmitting classified data to the Chinese government. She was accused of serving as a double agent for both China and the United States.
19. Karel Koecher
    a. Number of years conducting espionage: 11 years and 10 months
    b. Beginning date of espionage: February 1973
    c. Date of capture: November 27, 1984
    d. Country or organization spied for: Czechoslovakia
    Karel Koecher was an intelligence officer born in Czechoslovakia. During the Cold War, he served as a double agent for the CIA. Koecher penetrated the CIA in the 1960s and 1970s. He became the first-ever foreign secret agent to infiltrate America’s intelligence bureau at such a high position. Koecher’s spying acts consisted of sending highly confidential data to the KGB. In 1984, his double agent status was found. This event resulted in his capture and consequent prisoner swap between Czechoslovakia and the United States.
20. Jerry Alfred Whitworth
    a. Number of years conducting espionage: 10 years and 4 months
    b. Beginning date of espionage: February 1975
    c. Date of capture: June 3, 1985
    d. Country or organization spied for: USSR or the Soviet Union
    During the Cold War, Jerry Alfred Whitworth was a principal figure in one of the most notorious espionage groups, the “Walker Spy Ring.” Secret agent John Anthony Walker, Jr. (see number 16) spearheaded this organization and ran it for more than 10 years. Whitworth worked as a US Navy senior radio operator. His spying actions compromised US codes and considerably endangered American national security. In 1986, Whitworth was convicted for giving away sensitive data to the USSR in exchange for money and was sentenced to 365 years in jail.
21. Subrahmanyam Kota
    a. Number of years conducting espionage: 10
    b. Beginning date of espionage: 1985
    c. Date of capture: October 18, 1995
    d. Country or organization spied for: USSR or the Soviet Union
    Subrahmanyam Kota served as Boston Group’s president, helming this Massachusetts-based computer consultancy and placement company. In 1995, he was captured for his espionage ring involvement. The group sold highly confidential defense technology to the USSR’s KGB between 1985 and 1990. Kota sold stolen biotechnology material. Additionally, this secret agent sought to get details about semiconductor parts for infrared missile-tracking systems. Kota obtained information regarding mercury cadmium telluride missile detectors, which is the special coating for making stealth fighters undetectable to radars. An FBI sworn statement indicated that this spy convened with and gave away sensitive data to Russian spies in various foreign places, including Cyprus, Bermuda, Switzerland, and Portugal.
22. David Sheldon Boone
    a. Number of years conducting espionage: 10
    b. Beginning date of espionage: 1988
    c. Date of capture: October 10, 1998
    d. Country or organization spied for: USSR or the Soviet Union
    David Sheldon Boone served as a US Army signals analyst. From 1988 to 1991, he disseminated confidential files to the USSR in exchange for money. These classified documents comprised a handbook about how the United States planned to wage a nuclear battle. Boone performed his espionage activities while stationed in West Germany as the Cold War waned. In 1998, he was arrested for spying-related actions and consequently sentenced to 24 years and four months in federal jail.
23. Ali Abdelseoud Mohamed
    a. Number of years conducting espionage: 9
    b. Beginning date of espionage: 1989
    c. Date of capture: September 10, 1998
    d. Country or organization spied for: Al-Qaeda
    Ali Abdelseoud Mohamed worked as an Egyptian military officer and became a double agent for Al-Qaeda and the United States. Following his immigration to America, he served as an FBI whistleblower while furtively helping Al-Qaeda with training and strategic planning. Mohamed’s espionage activities comprised his involvement in the 1998 US Embassy shellings in East Africa and the 1993 World Trade Center bombing. This foreign-born American spy’s dual roles became completely understood after his capture. Mohamed’s case shed light on counterterrorism campaigns’ intricacies.
24. Aldrich Hazen Ames
    a. Number of years conducting espionage: 8 years and 11 months
    b. Beginning date of espionage: April 1985
    c. Date of capture: February 21, 1994
    d. Country or organization spied for: USSR or the Soviet Union
    Aldrich Hazen Ames’s espionage operations are considered among the most harmful in US intelligence history. This CIA officer who became a KGB mole was active during the Cold War’s latter half and many years later. From 1985 until Ames’s capture in 1994, he gave away sensitive details to the USSR. His betrayal of the US Government resulted in several US secret agents’ execution and the compromise of roughly 100 US intelligence operations.
25. Jeffrey Martin Carney
    a. Number of years conducting espionage: 8
    b. Beginning date of espionage: April 1983
    c. Date of capture: April 22, 1991
    d. Country or organization spied for: East Germany
    Jeffrey Martin Carney worked as a US Air Force intelligence specialist who served as a spy for East Germany during the Cold War. In the 1980s, this American secret agent gave away more than 100 confidential documents to the East German Ministry for State Security or Stasi, which was East Germany’s secret police. Carney’s espionage activities considerably compromised US national security. This enemy agent, who was characterized as a loner, performed his illegal activities while he was assigned to West Germany. Carney reportedly defected following his disenchantment with US military life. After the Berlin Wall’s demolition in 1989, the US Air Force Office of Special Investigations became aware of this American spy’s activities, which resulted in numerous Stasi records’ declassification. Carney was arrested in 1991 and sentenced to 38 years in federal prison.

In CEOWORLD Magazine’s list of the 25 Notorious Spies in American National Security History, readers will find that these infamous turncoats committed their crimes for many years and even decades. Because of these criminals’ desire for financial gain or their staunch belief in a particular ideology such as Communism, their spying activities resulted in the loss of many lives directly and indirectly. These dishonorable secret agents’ actions also led to tense relations between the United States and other foreign countries. On the other hand, these enemy spies made the United States’ defense and intelligence agencies work harder to strengthen their capabilities in combating these unscrupulous defectors.

Have you read?
Here’s Every Time the United States Sent Military Forces To China.
Most Powerful Companies in Australia, 2023.
The highest-paid tech CEOs in the United States.
Highest-Paid Biopharmaceutical CEOs in the United States.
Executive Pay: Top 8 Highest-Paid Hotel CEOs.
Openly LGBTQ CEOs at the helm of major global companies.