New York Consolidated Laws, Civil Practice Law and Rules - CVP § 1024. Unknown parties

A party who is ignorant, in whole or in part, of the name or identity of a person who may properly be made a party, may proceed against such person as an unknown party by designating so much of his name and identity as is known.  If the name or remainder of the name becomes known all subsequent proceedings shall be taken under the true name and all prior proceedings shall be deemed amended accordingly.