legitimate device registrations using microsoft authentication broker may occur during corporate enrollment scenarios or bulk provisioning, but it is uncommon for multiple source ips to register the same identity across microsoft graph, device registration service (drs), and azure active directory (aad) in a short time span.

Techniques

Sample rules

Suspicious Microsoft OAuth Flow via Auth Broker to DRS

source: elastic
technicques:
- T1078
- T1528
- T1566

Description

Identifies separate OAuth authorization flows in Microsoft Entra ID where the same user principal and session ID are observed across multiple IP addresses within a 5-minute window. These flows involve the Microsoft Authentication Broker (MAB) as the client application and the Device Registration Service (DRS) as the target resource. This pattern is highly indicative of OAuth phishing activity, where an adversary crafts a legitimate Microsoft login URL to trick a user into completing authentication and sharing the resulting authorization code, which is then exchanged for an access and refresh token by the attacker.

Detection logic

from logs-azure.signinlogs-* metadata _id, _version, _index
| where
    event.dataset == "azure.signinlogs" and
    event.outcome == "success" and
    azure.signinlogs.properties.user_type == "Member" and
    azure.signinlogs.identity is not null and
    azure.signinlogs.properties.user_principal_name is not null and
    source.address is not null and
    azure.signinlogs.properties.app_id == "29d9ed98-a469-4536-ade2-f981bc1d605e" and  // MAB
    azure.signinlogs.properties.resource_id == "01cb2876-7ebd-4aa4-9cc9-d28bd4d359a9"  // DRS

| eval
    Esql.time_window_date_trunc = date_trunc(30 minutes, @timestamp),
    Esql.azure_signinlogs_properties_session_id = azure.signinlogs.properties.session_id,
    Esql.is_browser_case = case(
        to_lower(azure.signinlogs.properties.device_detail.browser) rlike "(chrome|firefox|edge|safari).*", 1, 0
    )

| stats
    Esql_priv.azure_signinlogs_properties_user_display_name_values = values(azure.signinlogs.properties.user_display_name),
    Esql_priv.azure_signinlogs_properties_user_principal_name_values = values(azure.signinlogs.properties.user_principal_name),
    Esql.azure_signinlogs_properties_session_id_values = values(azure.signinlogs.properties.session_id),
    Esql.azure_signinlogs_properties_unique_token_identifier_values = values(azure.signinlogs.properties.unique_token_identifier),

    Esql.source_geo_city_name_values = values(source.geo.city_name),
    Esql.source_geo_country_name_values = values(source.geo.country_name),
    Esql.source_geo_region_name_values = values(source.geo.region_name),
    Esql.source_address_values = values(source.address),
    Esql.source_address_count_distinct = count_distinct(source.address),
    Esql.source_as_organization_name_values = values(source.`as`.organization.name),

    Esql.azure_signinlogs_properties_authentication_protocol_values = values(azure.signinlogs.properties.authentication_protocol),
    Esql.azure_signinlogs_properties_authentication_requirement_values = values(azure.signinlogs.properties.authentication_requirement),
    Esql.azure_signinlogs_properties_is_interactive_values = values(azure.signinlogs.properties.is_interactive),

    Esql.azure_signinlogs_properties_incoming_token_type_values = values(azure.signinlogs.properties.incoming_token_type),
    Esql.azure_signinlogs_properties_token_protection_status_details_sign_in_session_status_values = values(azure.signinlogs.properties.token_protection_status_details.sign_in_session_status),
    Esql.azure_signinlogs_properties_session_id_count_distinct = count_distinct(azure.signinlogs.properties.session_id),
    Esql.azure_signinlogs_properties_app_display_name_values = values(azure.signinlogs.properties.app_display_name),
    Esql.azure_signinlogs_properties_app_id_values = values(azure.signinlogs.properties.app_id),
    Esql.azure_signinlogs_properties_resource_id_values = values(azure.signinlogs.properties.resource_id),
    Esql.azure_signinlogs_properties_resource_display_name_values = values(azure.signinlogs.properties.resource_display_name),

    Esql.azure_signinlogs_properties_app_owner_tenant_id_values = values(azure.signinlogs.properties.app_owner_tenant_id),
    Esql.azure_signinlogs_properties_resource_owner_tenant_id_values = values(azure.signinlogs.properties.resource_owner_tenant_id),

    Esql.azure_signinlogs_properties_conditional_access_status_values = values(azure.signinlogs.properties.conditional_access_status),
    Esql.azure_signinlogs_properties_risk_state_values = values(azure.signinlogs.properties.risk_state),
    Esql.azure_signinlogs_properties_risk_level_aggregated_values = values(azure.signinlogs.properties.risk_level_aggregated),

    Esql.azure_signinlogs_properties_device_detail_browser_values = values(azure.signinlogs.properties.device_detail.browser),
    Esql.azure_signinlogs_properties_device_detail_operating_system_values = values(azure.signinlogs.properties.device_detail.operating_system),
    Esql.user_agent_original_values = values(user_agent.original),
    Esql.is_browser_case_max = max(Esql.is_browser_case),

    Esql.event_count = count(*)
  by
    Esql.time_window_date_trunc,
    azure.signinlogs.properties.user_principal_name,
    azure.signinlogs.properties.session_id

| keep
    Esql.time_window_date_trunc,
    Esql_priv.azure_signinlogs_properties_user_display_name_values,
    Esql_priv.azure_signinlogs_properties_user_principal_name_values,
    Esql.azure_signinlogs_properties_session_id_values,
    Esql.azure_signinlogs_properties_unique_token_identifier_values,
    Esql.source_geo_city_name_values,
    Esql.source_geo_country_name_values,
    Esql.source_geo_region_name_values,
    Esql.source_address_values,
    Esql.source_address_count_distinct,
    Esql.source_as_organization_name_values,
    Esql.azure_signinlogs_properties_authentication_protocol_values,
    Esql.azure_signinlogs_properties_authentication_requirement_values,
    Esql.azure_signinlogs_properties_is_interactive_values,
    Esql.azure_signinlogs_properties_incoming_token_type_values,
    Esql.azure_signinlogs_properties_token_protection_status_details_sign_in_session_status_values,
    Esql.azure_signinlogs_properties_session_id_count_distinct,
    Esql.azure_signinlogs_properties_app_display_name_values,
    Esql.azure_signinlogs_properties_app_id_values,
    Esql.azure_signinlogs_properties_resource_id_values,
    Esql.azure_signinlogs_properties_resource_display_name_values,
    Esql.azure_signinlogs_properties_app_owner_tenant_id_values,
    Esql.azure_signinlogs_properties_resource_owner_tenant_id_values,
    Esql.azure_signinlogs_properties_conditional_access_status_values,
    Esql.azure_signinlogs_properties_risk_state_values,
    Esql.azure_signinlogs_properties_risk_level_aggregated_values,
    Esql.azure_signinlogs_properties_device_detail_browser_values,
    Esql.azure_signinlogs_properties_device_detail_operating_system_values,
    Esql.user_agent_original_values,
    Esql.is_browser_case_max,
    Esql.event_count

| where
    Esql.source_address_count_distinct >= 2 and
    Esql.azure_signinlogs_properties_session_id_count_distinct == 1 and
    Esql.is_browser_case_max >= 1 and
    Esql.event_count >= 2