The Okta Potentially Stolen Session rule identifies potentially compromised user sessions by detecting logins to an Okta account from different devices simultaneously. This can indicate session token theft, where an attacker uses the same valid session from multiple locations. The detection is based on analyzing the Okta System Log for events that show a user logged into the same account from distinct, unrecognized machines at the same time, prompting further investigation and potential account lockout to mitigate risk. The validation process involves reviewing the device types, geographic locations, and other session-related data, which can help determine the legitimacy of the logins.