The exploit used, named EternalBlue, exploits a vulnerability in the Server Message Block (SMB) protocol which allows the malware to spread to all unpatched Windows systems from XP to 2016 on a network that have this protocol enabled. This vulnerability allows remote code execution over SMB v1. WannaCry utilizes this exploit by crafting a custom SMB session request with hard-coded values based on the target system. Notably, after the first SMB packet sent to the victim’s IP address, the malware sends two additional packets to the victim containing the hard-coded IP addresses 192.168.56.20 and 172.16.99.5