Techniques
Sample rules
O365 High Number Of Failed Authentications for User
- source: splunk
- technicques:
- T1110
- T1110.001
Description
The following analytic identifies an O365 account that has experienced more than 20 failed authentication events within a span of 5 minutes. This could be indicative of an attacker attempting to brute force or guess the password for that particular user account. It leverages the O365 Unified Audit Logs, specifically the “UserLoginFailed” events. By monitoring the frequency and volume of these events for individual users, the analytic can flag accounts that exceed the set threshold of failed attempts within the defined timeframe. Multiple failed login attempts in a short period can be a strong indicator of malicious activity. While there could be benign reasons, such as a user forgetting their password, the rapid succession of failed attempts is often a sign of an attacker trying to gain unauthorized access. By detecting and alerting on this behavior, the SOC can quickly investigate and take appropriate action, potentially stopping an attack in its early stages. Given that environments differ across organizations, security teams should consider customizing the threshold of this detection to better suit their specific needs and risk profile. If an attacker successfully guesses or brute-forces a user’s password after numerous attempts, they can gain unauthorized access to the O365 environment. This unauthorized access could allow them to view sensitive emails, documents, and other data.
Detection logic
`o365_management_activity` Operation=UserLoginFailed record_type=AzureActiveDirectoryStsLogon Workload=AzureActiveDirectory
| bucket span=5m _time
| stats dc(_raw) AS failed_attempts values(src_ip) as src_ip by user, _time
| where failed_attempts > 10
| `o365_high_number_of_failed_authentications_for_user_filter`