Counterintelligence (noun)

1. Activities aimed at preventing foreign intelligence services from successfully gathering and collecting intelligence against one's country.
2. The branch of intelligence gathering and analysis concerned with identifying and neutralizing the efforts of foreign intelligence services.

Origin:

Derived from the combination of 'counter' meaning 'opposite' and 'intelligence' meaning 'information gathering and analysis.'.

Examples:

1. The counterintelligence division of the FBI is responsible for protecting the United States against espionage and other intelligence activities by foreign governments.
2. Counterintelligence activities can include physical and electronic surveillance, recruitment of spies and double agents, and covert operations.
3. Many countries have established counterintelligence agencies to safeguard their national security interests.
4. The failure of counterintelligence was a major factor in the success of the September 11th attacks.
5. Counterintelligence activities are often shrouded in secrecy and not much is known to the public about their operations.