This query is designed to identify successful sign-ins to Azure Active Directory from countries that have not been previously observed within a specified timeframe. The purpose is to detect potentially suspicious activity, such as an unauthorized user accessing an account from a new location.

Here's a simplified breakdown:

1. Purpose: The query aims to find successful login attempts from countries that have not been seen before in the user's login history.

2. Data Source: The query uses sign-in logs from Azure Active Directory. There are two versions of the query: one for Microsoft 365 Defender (M365D) and another for Microsoft Sentinel.

3. Lookback Period:

   • M365D: Considers login data from the past 30 days, excluding the last 3 days.
   • Sentinel: Considers login data from the past 90 days, excluding the last 3 days.

4. Process:

   • First, it identifies all countries from which successful logins have occurred within the lookback period (excluding the last 3 days).
   • Then, it checks for any successful logins in the last 3 days from countries not in the previously identified list.

5. Output: The query outputs details of these new-country logins, including the timestamp, country, user agent, error code, account information, and IP address.

6. Risk: The detection of a login from a new country could indicate unauthorized access, suggesting that an adversary might be attempting to access the account from a different location.

In summary, this query helps in identifying potentially unauthorized access attempts by flagging successful logins from new countries, which could be indicative of a security risk.