insider

An accepted member of a group.

One who has special knowledge or access to confidential information.

One who is inside; one who is within the limits of some place, structure, society, organization (as a church), etc.

Hence One who has some special advantage, as in a business enterprise.

an officer of a corporation or others who have access to private information about the corporation’s operations, especially information relating to profitability.

A person who has special knowledge about the inner workings of a group, organization, or institution.

A person who is within an enclosed space.

an officer of a corporation or others who have access to private information about the corporation’s operations