spies

Spies are individuals who obtain or convey information that is secret or sensitive, typically for a government, military, or other organization. Espionage is the practice of gathering, transmitting, or using such information by covert means, often in pursuit of national security, military advantage, or competitive intelligence.

Most espionage relies on human sources (HUMINT), clandestine recruitment, and covert reporting. Other methods involve signals intelligence, cyber operations, and the analysis of publicly available information when used covertly (open-source intelligence).

Spying has a long history, with practice attested in ancient Egypt, Persia, Greece, and Rome, through medieval courts and early modern states. The modern era saw formal intelligence services and large networks; the Cold War popularized espionage as a central element of international competition, featuring double agents and high-profile defections.

Today, many countries maintain agencies that recruit, manage, and protect sources of information. Espionage remains legally complex, as governments justify it for security while laws and norms restrict illegal activity; casualties and prosecutions occur when spies are uncovered.

Notable cases include Mata Hari, who operated during World War I; Richard Sorge, a Soviet journalist-turned-spy in Japan during World War II; and Western defectors such as Kim Philby, Aldrich Ames, Robert Hanssen, and Oleg Penkovsky.

Spying is not limited to governments; corporate espionage targets companies and trade secrets, while counterintelligence aims to detect, deter, and respond to spies.