The client and server are communicating over the SMB Protocol. When printing a document a person may use their computer, the client, to send a request to a colleague’s computer, the server, with a request to print the document. The SMB Protocol is a standard, generally secure system that creates a connection between client and server by sending responses and requests. These data packets can contain malware such as a trojan, ransomware or similar dangerous program.

This dupes a Windows machine that has not been patched against the vulnerability into allowing illegitimate data packets into the legitimate network. EternalBlue is a Windows exploit created by the US National Security Agency (NSA) and used in the 2017 WannaCry ransomware attack.ĮternalBlue exploits a vulnerability in the Microsoft implementation of the Server Message Block (SMB) Protocol.