The Chinese hacking group that co-opted the N.S.A.'s tools is considered by the agency's analysts to be among the most dangerous Chinese contractors it tracks, according to a classified agency memo reviewed by The New York Times. The group is responsible for numerous attacks on some of the most sensitive defense targets inside the United States, including space, satellite and nuclear propulsion technology makers. -New York Times

The swiped software (Backdoor.Doublepulsar) and its "custom exploit tool" installation software (Trojan.Bemstour) infects a computer's memory, and remains even if DoublePulsar is removed. According to Symantec, these tools were used by the Chinese hacking group in 2016 (and shortly after leaked to the public by a group calling itself the Shadow Brokers). 

Bemstour exploits two Windows vulnerabilities in order to achieve remote kernel code execution on targeted computers. One vulnerability is a Windows zero-day vulnerability (CVE-2019-0703) discovered by Symantec. The second Windows vulnerability (CVE-2017-0143) was patched in March 2017 after it was discovered to have been used by two exploit tools—EternalRomance and EternalSynergy—that were also released as part of the Shadow Brokers leak.