Understanding Office 365 Cloud App Security Log Examples

Key Log Types in Office 365 Cloud App Security

Office 365 Cloud App Security (CAS) generates several log categories that feed the security dashboard: alerts triggered by policy violations, activity logs for user and admin actions, data‑exfiltration events, and integration logs from connected services. Each log entry records a timestamp, user or device ID, action performed, risk score, and a JSON payload with contextual details.

Typical Alert Log Example

An alert log appears when a policy, such as "Impossible Travel," fires. Example JSON excerpt:

• {"timestamp":"2024-03-15T08:42:10Z","alertId":"A12345","policy":"ImpossibleTravel","user":"john.doe@contoso.com","riskScore":85,"location":"Tokyo, JP","previousLocation":"New York, US","details":"Login from two continents within 30 minutes."}

This entry lets analysts see the user, the anomalous locations, and the severity, enabling rapid investigation.

User Activity Log Example

Activity logs capture routine actions like file sharing or mailbox access. Example:

• {"timestamp":"2024-03-14T14:07:33Z","activityId":"U98765","user":"jane.smith@contoso.com","action":"FileDownloaded","resource":"/Shared/QuarterlyReport.xlsx","ip":"192.168.10.22","client":"OneDriveWeb"}

Correlating activity logs with alerts helps determine whether a flagged event is part of normal behavior.

Data Exfiltration Log Example

When a DLP policy detects sensitive data movement, CAS logs the event. Example entry:

• {"timestamp":"2024-03-13T22:18:05Z","eventId":"D45678","policy":"CreditCardLeak","user":"mark.taylor@contoso.com","file":"/Finance/Invoices/2024/Q1.pdf","sensitivity":"PCI","action":"SharedExternally","recipients":["partner@example.org"],"riskScore":92}

This provides the file path, sensitivity label, and external recipients, essential for containment.

Integration Log Example

CAS can forward logs to SIEMs via Azure Sentinel or third‑party solutions. An integration log shows the transmission status:

• {"timestamp":"2024-03-15T00:00:00Z","integration":"AzureSentinel","status":"Success","recordsSent":1245,"errorMessage":null}

Monitoring integration logs ensures that no data is lost between CAS and downstream analytics.

Comparing Log Attributes

Practical Tips for Analyzing CAS Logs

• Filter by riskScore ≥ 70 to prioritize high‑impact alerts.• Correlate user activity logs within a 15‑minute window before and after an alert to spot compromised credentials.• Use the "resource" field to map file paths to SharePoint or OneDrive sites for rapid containment.• Export logs to a SIEM and apply UEBA rules for anomaly scoring across the entire Office 365 tenant.• Regularly audit integration logs to verify that no records fail to reach the SIEM.