The 'Microsoft 365 Impossible Travel Activity' detection rule is designed to identify anomalous user sign-in attempts flagged by Microsoft Cloud App Security, specifically where a user appears to log in from geographically distant locations in a short timeframe—known as impossible travel. This situation often indicates potential credential compromise, where attackers leveraging stolen credentials could gain unauthorized access. The rule triggers based on successful login events that are inconsistent with recognized user behavior, particularly when such activations are recorded in the Microsoft 365 audit logs. Analysts are guided to conduct a thorough investigation by cross-referencing login events, examining audit logs to identify the specifics of each occurrence—including the time, IP addresses, and historical context of the account. Additional guidance includes administering user notifications, implementing multi-factor authentication for at-risk accounts, and scrutinizing this detection for common false positives like regular travel patterns and VPN usage. Furthermore, the rule covers associated response measures, such as account isolation and security posture improvements following an incident. As of the creation of this rule, practitioners are advised to consider its reduced relevance due to updates in Microsoft Defender for Office 365 and consult overlapping detection rules for improved coverage.