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Microsoft Entra ID Sign-In Brute Force Activity

Identifies potential brute-force attacks targeting user accounts by analyzing failed sign-in patterns in Microsoft Entra ID Sign-In Logs. This detection focuses on a high volume of failed interactive or non-interactive authentication attempts within a short time window, often indicative of password spraying, credential stuffing, or password guessing. Adversaries may use these techniques to gain unauthorized access to applications integrated with Entra ID or to compromise valid user accounts.

Rule type: esql
Rule indices:

Rule Severity: medium
Risk Score: 47
Runs every: 15m
Searches indices from: now-60m
Maximum alerts per execution: ?
References:

Tags:

  • Domain: Cloud
  • Domain: Identity
  • Data Source: Azure
  • Data Source: Entra ID
  • Data Source: Entra ID Sign-in Logs
  • Use Case: Identity and Access Audit
  • Use Case: Threat Detection
  • Tactic: Credential Access
  • Resources: Investigation Guide

Version: ?
Rule authors:

  • Elastic

Rule license: Elastic License v2

This rule detects brute-force authentication activity in Entra ID sign-in logs. It classifies failed sign-in attempts into behavior types such as password spraying, credential stuffing, or password guessing. The classification (bf_type) helps prioritize triage and incident response.

  • Review bf_type: Determines the brute-force technique being used (password_spraying, credential_stuffing, or password_guessing).
  • Examine user_id_list: Identify if high-value accounts (e.g., administrators, service principals, federated identities) are being targeted.
  • Review login_errors: Repetitive error types like "Invalid Grant" or "User Not Found" suggest automated attacks.
  • Check ip_list and source_orgs: Investigate if the activity originates from suspicious infrastructure (VPNs, hosting providers, etc.).
  • Validate unique_ips and countries: Geographic diversity and IP volume may indicate distributed or botnet-based attacks.
  • Compare total_attempts vs duration_seconds: High rate of failures in a short time period implies automation.
  • Analyze user_agent.original and device_detail_browser: User agents like curl, Python, or generic libraries may indicate scripting tools.
  • Investigate client_app_display_name and incoming_token_type: Detect potential abuse of legacy or unattended login mechanisms.
  • Inspect target_resource_display_name: Understand what application or resource the attacker is trying to access.
  • Pivot using session_id and device_detail_device_id: Determine if a device is targeting multiple accounts.
  • Review conditional_access_status: If not enforced, ensure Conditional Access policies are scoped correctly.
  • Legitimate automation (e.g., misconfigured scripts, sync processes) can trigger repeated failures.
  • Internal red team activity or penetration tests may mimic brute-force behaviors.
  • Certain service accounts or mobile clients may generate repetitive sign-in noise if not properly configured.
  • Notify your identity security team for further analysis.
  • Investigate and lock or reset impacted accounts if compromise is suspected.
  • Block offending IPs or ASNs at the firewall, proxy, or using Conditional Access.
  • Confirm MFA and Conditional Access are enforced for all user types.
  • Audit targeted accounts for credential reuse across services.
  • Implement account lockout or throttling for failed sign-in attempts where possible.
from logs-azure.signinlogs-*

// Define a time window for grouping and maintain the original event timestamp
| eval Esql.time_window_date_trunc = date_trunc(15 minutes, @timestamp)

// Filter relevant failed authentication events with specific error codes
| where event.dataset == "azure.signinlogs"
    and event.category == "authentication"
    and azure.signinlogs.category in ("NonInteractiveUserSignInLogs", "SignInLogs")
    and event.outcome == "failure"
    and azure.signinlogs.properties.authentication_requirement == "singleFactorAuthentication"
    and azure.signinlogs.properties.status.error_code in (
        50034,
        50126,
        50055,
        50056,
        50057,
        50064,
        50076,
        50079,
        50105,
        70000,
        70008,
        70043,
        80002,
        80005,
        50144,
        50135,
        50142,
        120000,
        120002,
        120020
    )
    and azure.signinlogs.properties.user_principal_name is not null and azure.signinlogs.properties.user_principal_name != ""
    and user_agent.original != "Mozilla/5.0 (compatible; MSAL 1.0) PKeyAuth/1.0"
    and source.`as`.organization.name != "MICROSOFT-CORP-MSN-as-BLOCK"

| stats
    Esql.azure_signinlogs_properties_authentication_requirement_values = values(azure.signinlogs.properties.authentication_requirement),
    Esql.azure_signinlogs_properties_app_id_values = values(azure.signinlogs.properties.app_id),
    Esql.azure_signinlogs_properties_app_display_name_values = values(azure.signinlogs.properties.app_display_name),
    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_conditional_access_status_values = values(azure.signinlogs.properties.conditional_access_status),
    Esql.azure_signinlogs_properties_device_detail_browser_values = values(azure.signinlogs.properties.device_detail.browser),
    Esql.azure_signinlogs_properties_device_detail_device_id_values = values(azure.signinlogs.properties.device_detail.device_id),
    Esql.azure_signinlogs_properties_device_detail_operating_system_values = values(azure.signinlogs.properties.device_detail.operating_system),
    Esql.azure_signinlogs_properties_incoming_token_type_values = values(azure.signinlogs.properties.incoming_token_type),
    Esql.azure_signinlogs_properties_risk_state_values = values(azure.signinlogs.properties.risk_state),
    Esql.azure_signinlogs_properties_session_id_values = values(azure.signinlogs.properties.session_id),
    Esql.azure_signinlogs_properties_user_id_values = values(azure.signinlogs.properties.user_id),
    Esql_priv.azure_signinlogs_properties_user_principal_name_values = values(azure.signinlogs.properties.user_principal_name),
    Esql.azure_signinlogs_result_description_values = values(azure.signinlogs.result_description),
    Esql.azure_signinlogs_result_signature_values = values(azure.signinlogs.result_signature),
    Esql.azure_signinlogs_result_type_values = values(azure.signinlogs.result_type),

    Esql.azure_signinlogs_properties_user_id_count_distinct = count_distinct(azure.signinlogs.properties.user_id),
    Esql.azure_signinlogs_properties_user_id_list = values(azure.signinlogs.properties.user_id),
    Esql.azure_signinlogs_result_description_values_all = values(azure.signinlogs.result_description),
    Esql.azure_signinlogs_result_description_count_distinct = count_distinct(azure.signinlogs.result_description),
    Esql.azure_signinlogs_properties_status_error_code_values = values(azure.signinlogs.properties.status.error_code),
    Esql.azure_signinlogs_properties_status_error_code_count_distinct = count_distinct(azure.signinlogs.properties.status.error_code),
    Esql.azure_signinlogs_properties_incoming_token_type_values_all = values(azure.signinlogs.properties.incoming_token_type),
    Esql.azure_signinlogs_properties_app_display_name_values_all = values(azure.signinlogs.properties.app_display_name),
    Esql.source_ip_values = values(source.ip),
    Esql.source_ip_count_distinct = count_distinct(source.ip),
    Esql.source_as_organization_name_values = values(source.`as`.organization.name),
    Esql.source_geo_country_name_values = values(source.geo.country_name),
    Esql.source_geo_country_name_count_distinct = count_distinct(source.geo.country_name),
    Esql.source_as_organization_name_count_distinct = count_distinct(source.`as`.organization.name),
    Esql.timestamp_first_seen = min(@timestamp),
    Esql.timestamp_last_seen = max(@timestamp),
    Esql.event_count = count()
by Esql.time_window_date_trunc

| eval
    Esql.duration_seconds = date_diff("seconds", Esql.timestamp_first_seen, Esql.timestamp_last_seen),
    Esql.brute_force_type = case(
        Esql.azure_signinlogs_properties_user_id_count_distinct >= 10 and Esql.event_count >= 30 and Esql.azure_signinlogs_result_description_count_distinct <= 3
            and Esql.source_ip_count_distinct >= 5
            and Esql.duration_seconds <= 600
            and Esql.azure_signinlogs_properties_user_id_count_distinct > Esql.source_ip_count_distinct,
        "credential_stuffing",

        Esql.azure_signinlogs_properties_user_id_count_distinct >= 15 and Esql.azure_signinlogs_result_description_count_distinct == 1 and Esql.event_count >= 15 and Esql.duration_seconds <= 1800,
        "password_spraying",

        (Esql.azure_signinlogs_properties_user_id_count_distinct == 1 and Esql.azure_signinlogs_result_description_count_distinct == 1 and Esql.event_count >= 30 and Esql.duration_seconds <= 300)
            or (Esql.azure_signinlogs_properties_user_id_count_distinct <= 3 and Esql.source_ip_count_distinct > 30 and Esql.event_count >= 100),
        "password_guessing",

        "other"
    )

| keep
    Esql.time_window_date_trunc,
    Esql.brute_force_type,
    Esql.duration_seconds,
    Esql.event_count,
    Esql.timestamp_first_seen,
    Esql.timestamp_last_seen,
    Esql.azure_signinlogs_properties_user_id_count_distinct,
    Esql.azure_signinlogs_properties_user_id_list,
    Esql.azure_signinlogs_result_description_values_all,
    Esql.azure_signinlogs_result_description_count_distinct,
    Esql.azure_signinlogs_properties_status_error_code_count_distinct,
    Esql.azure_signinlogs_properties_status_error_code_values,
    Esql.azure_signinlogs_properties_incoming_token_type_values_all,
    Esql.azure_signinlogs_properties_app_display_name_values_all,
    Esql.source_ip_values,
    Esql.source_ip_count_distinct,
    Esql.source_as_organization_name_values,
    Esql.source_geo_country_name_values,
    Esql.source_geo_country_name_count_distinct,
    Esql.source_as_organization_name_count_distinct,
    Esql.azure_signinlogs_properties_authentication_requirement_values,
    Esql.azure_signinlogs_properties_app_id_values,
    Esql.azure_signinlogs_properties_app_display_name_values,
    Esql.azure_signinlogs_properties_resource_id_values,
    Esql.azure_signinlogs_properties_resource_display_name_values,
    Esql.azure_signinlogs_properties_conditional_access_status_values,
    Esql.azure_signinlogs_properties_device_detail_browser_values,
    Esql.azure_signinlogs_properties_device_detail_device_id_values,
    Esql.azure_signinlogs_properties_device_detail_operating_system_values,
    Esql.azure_signinlogs_properties_incoming_token_type_values,
    Esql.azure_signinlogs_properties_risk_state_values,
    Esql.azure_signinlogs_properties_session_id_values,
    Esql.azure_signinlogs_properties_user_id_values,
    Esql_priv.azure_signinlogs_properties_user_principal_name_values,
    Esql.azure_signinlogs_result_description_values,
    Esql.azure_signinlogs_result_signature_values,
    Esql.azure_signinlogs_result_type_values

| where Esql.brute_force_type != "other"
  1. UserAccountNotFound
  2. InvalidUsernameOrPassword
  3. PasswordExpired
  4. InvalidPassword
  5. UserDisabled
  6. CredentialValidationFailure
  7. MFARequiredButNotPassed
  8. MFARegistrationRequired
  9. EntitlementGrantsNotFound
  10. InvalidGrant
  11. ExpiredOrRevokedRefreshToken
  12. BadTokenDueToSignInFrequency
  13. OnPremisePasswordValidatorRequestTimedOut
  14. OnPremisePasswordValidatorUnpredictableWebException
  15. InvalidPasswordExpiredOnPremPassword
  16. PasswordChangeCompromisedPassword
  17. PasswordChangeRequiredConditionalAccess
  18. PasswordChangeIncorrectCurrentPassword
  19. PasswordChangeInvalidNewPasswordWeak
  20. PasswordChangeFailure

Framework: MITRE ATT&CK