N.Y. Real Prop. Acts. Law § 225

§ 225. Notice of action adverse to possession of tenant. Where a\nprocess or summons in an action to recover the real property occupied by\nhim, or the possession thereof, is served upon a tenant, he must\nforthwith give notice thereof to his landlord; otherwise he forfeits the\nvalue of three years' rent of such property, to the landlord or other\nperson of whom he holds.\n