US Patent 11995186 Ransomware attack onset detection

A method of detecting the onset of a ransomware attack is presented. In an example embodiment, file backup metadata for each of a plurality of computing devices is accessed and analyzed to detect anomalous file backup activity of individual ones of the computing devices. A determination is made as to whether the detected anomalous file backup activity of at least some of the computing devices is correlated in time. File description metadata for each of the computing devices is also accessed and analyzed to identify files in the computing devices that are anomalous to other files in the computing devices. A determination whether a ransomware attack has begun is based on a determination that the detected anomalous file backup activity of at least some of the computing devices is correlated in time, as well as on the identified anomalous files.