EternalBlue, sometimes stylized as ETERNALBLUE, is an exploit developed by the U.S. National Security Agency (NSA) according to testimony by former NSA employees. It was leaked by the Shadow Brokers hacker group on April 14, 2017, and was used as part of the worldwide WannaCry ransomware attack on May 12, 2017. The exploit was also used to help carry out the 2017 NotPetya cyberattack on June 27, 2017 and reported to be used as part of the Retefe banking trojan since at least September 5, 2017.
EternalBlue exploits a vulnerability in Microsoft's implementation of the Server Message Block (SMB) protocol. This vulnerability is denoted by entry CVE-2017-0144 in the Common Vulnerabilities and Exposures (CVE) catalog. The vulnerability exists because the SMB version 1 (SMBv1) server in various versions of Microsoft Windows mishandles specially crafted packets from remote attackers, allowing them to execute arbitrary code on the target computer.
The NSA eventually warned Microsoft after learning about EternalBlue’s possible theft, allowing the company to prepare a software patch issued in March 2017, after cancelling all security patches in February 2017. On Tuesday, March 14, 2017, Microsoft issued security bulletin MS17-010, which detailed the flaw and announced that patches had been released for all Windows versions that were currently supported at that time, these being Windows 7, Windows 8.1, Windows 10, Windows Server 2008, Windows Server 2012, and Windows Server 2016, as well as Windows Vista (which had recently ended support). Many Windows users had not installed the patches when, two months later on May 12, 2017, the WannaCry ransomware attack used the EternalBlue vulnerability to spread itself. The next day, Microsoft released emergency security patches for Windows 7 and Windows 8, and the unsupported Windows XP and Windows Server 2003.
In February 2018, EternalBlue was ported to all Windows operating systems since Windows 2000 by RiskSense security researcher Sean Dillon. EternalChampion and EternalRomance, two other exploits originally developed by the NSA and leaked by The Shadow Brokers, were also ported at the same event. They were made available as open sourced Metasploit modules.
By the end of 2018, millions of systems were still vulnerable to EternalBlue. This has led to millions of dollars in damages due primarily to ransomware worms. Following the massive impact of WannaCry, both NotPetya and BadRabbit caused over $1 billion worth of damages in over 65 countries, using EternalBlue as either an initial compromise vector or as a method of lateral movement. 
According to Microsoft, it was the US's NSA that was responsible, by dint of its controversial strategy of "stockpiling of vulnerabilities", for, at the least, preventing Microsoft from timely public patching of this, and presumably other, hidden bugs.
EternalRocks or MicroBotMassiveNet is a computer worm that infects Microsoft Windows. It uses seven exploits developed by the NSA. Comparatively, the WannaCry ransomware program that infected 230,000 computers in May 2017 only uses two NSA exploits, making researchers believe EternalRocks to be significantly more dangerous. The worm was discovered via honeypot.
EternalRocks first installs Tor, a private network that conceals Internet activity, to access its hidden servers. After a brief 24 hour "incubation period", the server then responds to the malware request by downloading and self-replicating on the "host" machine.
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