All-time biggest ransomware attacks worldwide 2025

As of July 2025, the WannaCry ransomware attack launched in 2017 was the biggest attack by its impact. During this attack, cyber actors took over 250 thousand user accounts of Microsoft Windows. As a result of this attack, the company lost over four billion U.S. dollars. The latest of selected significant cyberattacks was the 2022 ransomware attack against Swisspost, in which 1.6 terabytes of data was stolen.