New York Civil Practice Law & Rules Section 1024 - Unknown parties.

 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.

Last modified: February 3, 2019