What is your definition of counterintelligence?

According to the Central Intelligence Agency, Counterintelligence is the study of the organization and behavior of the intelligence services of foreign states and entities, and the application of the resulting knowledge.

Counterintelligence or (CI) refers to efforts made by intelligence organizations to prevent hostile or enemy intelligence organizations from successfully gathering and collecting intelligence against them. National intelligence programs by extension are the overall defenses of nations. Every nation is vulnerable to attack.  It is the role of intelligence cycle security to protect the process embodied in the intelligence cycle, and that which it defends.  A number of disciplines go into protecting the intelligence cycle. One of the challenges is there is a wide range of potential threats so threat assessments must be completed.

Many governments organize counterintelligence agencies separate and distinct from their intelligence collection services for specialized purposes. In most countries the counterintelligence mission is spread over multiple organizations, though one usually predominates. There is usually a domestic counterintelligence service, perhaps part of a larger law enforcement organization such as the Federal Bureau of Investigation in the United States. Military organizations have their own counterintelligence forces, capable of conducting protective operations both at home and when deployed abroad. Depending on the country, there can be various mixtures of civilian and military in foreign operations.

My definition of counterintelligence is, information gathered and activities conducted to protect against espionage, foreign intelligence gathering activities, sabotage, or assassinations conducted by or on behalf of foreign governments or elements thereof, foreign organizations, or foreign persons, or international terrorist activities.