DoublePulsar is a backdoor implant tool developed by the U.S. National Security Agency's (NSA) Equation Group that was leaked by The Shadow Brokers in early 2017. The tool infected more than 200,000 Microsoft Windows computers in only a few weeks, and was used alongside EternalBlue in the May 2017 WannaCry ransomware attack. A variant of DoublePulsar was first seen in the wild in March 2016, as discovered by Symantec.