OneLogin User Assumed Another User

AnalysisType: rule
Filename: onelogin_user_assumed.py
RuleID: "OneLogin.UserAssumption"
DisplayName: "OneLogin User Assumed Another User"
Enabled: true
LogTypes:
  - OneLogin.Events
Tags:
  - OneLogin
  - Lateral Movement:Use Alternate Authentication Material
Reports:
  MITRE ATT&CK:
    - TA0008:T1550
Severity: Low
Description: User assumed another user account
Reference: https://onelogin.service-now.com/kb_view_customer.do?sysparm_article=KB0010594#:~:text=Prerequisites,Actions%20and%20select%20Assume%20User.
Runbook: >
  Investigate whether this was authorized access.
SummaryAttributes:
  - account_id
  - user_name
  - user_id
Tests:
  - Name: User assumed their own account
    ExpectedResult: false
    Log:
      {
        "event_type_id": "240",
        "actor_user_id": 123456,
        "actor_user_name": "Bob Cat",
        "user_id": 123456,
        "user_name": "Bob Cat",
      }
  - Name: User assumed another user's account
    ExpectedResult: true
    Log:
      {
        "event_type_id": "3",
        "actor_user_id": 654321,
        "actor_user_name": "Mountain Lion",
        "user_id": 123456,
        "user_name": "Bob Cat",
      }


# ------ paired body: onelogin_user_assumed.py ------

def rule(event):
    # check that this is a user assumption event; event id 3
    return str(event.get("event_type_id")) == "3" and event.get(
        "actor_user_id", "UNKNOWN_USER"
    ) != event.get("user_id", "UNKNOWN_USER")


def title(event):
    return (
        f"A user [{event.get('actor_user_name', '<UNKNOWN_USER>')}] assumed another user "
        f"[{event.get('user_name', '<UNKNOWN_USER>')}] account"
    )