Espionage

Espionage is the practice of obtaining secret or confidential information without the permission of its holder. It is typically associated with national security, but corporate and organizational espionage also occur. Espionage involves covert collection, recruitment of agents, deception, and the use of various techniques to acquire information that is not publicly available.

Historically, espionage has existed in many cultures. In modern times it expanded with the rise of professional intelligence services in the 19th and 20th centuries, intensifying during the world wars and the Cold War. Advances in communications, signals intelligence, and surveillance transformed the field, culminating in cyber espionage in the 21st century.

Common methods include human intelligence (agents and defectors), signals intelligence (intercepted communications and telemetry), open-source intelligence, and cyber operations using malware, phishing, and intrusions. Financial influence, forgery, and the use of double agents have also been employed to shape outcomes.

Espionage is illegal in many jurisdictions when conducted without authorization, and many countries distinguish between intelligence gathering during war and peacetime. Laws such as treason or espionage statutes regulate or criminalize unauthorized spying; individuals may be prosecuted, imprisoned, or executed in extreme cases.

Counterintelligence and security measures aim to detect and deter espionage, including background checks, compartmentalization, secure communications, encryption, monitoring, and rapid incident response. International norms are limited, and states often deny involvement or justify covert operations.

Notable cases include Kim Philby, Anthony Blunt, and the Cambridge Spy Ring; Julius and Ethel Rosenberg; Aldrich Ames; and Robert Hanssen. In recent decades disclosures by Chelsea Manning and Edward Snowden have highlighted large-scale intelligence operations.

Today, espionage combines traditional human and signals intelligence with cyber operations and economic or industrial espionage. State actors, proxies, and criminal groups conduct campaigns that complicate defense and diplomacy, making counterintelligence a central concern of national security.