Suspicious File Renames Indicative of Ransomware
This rule detects a high volume of file rename events where the new file extension is not a commonly known good extension. This behavior is often associated with ransomware encrypting files and changing their extensions, or other forms of data destruction. The rule filters out common system directories to reduce false positives and aggregates events by process and device to identify the source of the suspicious activity.
Microsoft Sentinel (KQL)

