Explanation:

Below is the completed KQL that meets the requirement (successful sign-ins from multiple countries in the last 3 hours), using the ASIM authent ication schema commonly used in Microsoft Sentinel:
let timeframe = ago(3h);
let threshold = 5;
imAuthentication
| where TimeGenerated > timeframe
| where EventType == " Logon " and EventResult == " Success "
| where isnotempty(SrcGeoCountry)
| summarize
StartTime = min(TimeGenerated),
EndTime = max(TimeGenerated),
Vendors = make_set(EventVendor),
Products = make_set(EventProduct),
NumOfCountries = dcount(SrcGeoCountry)
by TargetUserId, TargetUserPrincipalName, TargetUserType
| where NumOfCountries > threshold
* Blade/source: imAuthentication (ASIM parser) normalizes authentication data across sources in Sentinel, letting you query sign-ins consistently.
* Filters: EventType == " Logon " and EventResult == " Success " restrict to successful l ogons.
* Geo dimension: SrcGeoCountry is the normalized source country field for the sign-in.
* Logic: We look back 3 hours , count distinct countries per user with dcount(SrcGeoCountry) , and keep only users exceeding a chosen threshold (e.g., > 5 ).
This delive rs exactly "successful sign-ins from multiple countries during the last three hours," ready for use in a hunting query or to form a scheduled analytics rule.