In The Matrix (1999), the hacker who betrays Neo’s group to Agent Smith is Cypher.
Cypher is a member of Morpheus’s resistance crew who has become disillusioned with life outside the simulated world. He secretly negotiates with Agent Smith, hoping to be reinserted into the Matrix with his memories erased. His betrayal endangers the entire crew and becomes one of the film’s major internal conflicts.
Joe Pantoliano plays Cypher, while Hugo Weaving plays Agent Smith. The character’s name is a variation of “cipher,” a term associated with codes and secret communication, matching the film’s recurring language of encryption, identity, and hidden systems.
Cypher is sometimes confused with the film’s other crew members, such as Tank, Apoc, or Mouse. Unlike them, he actively works against Morpheus’s team and helps Smith locate their ship and operators.