Detect Multi-Factor Authentication Interception in Elastic Security
Adversaries may target multi-factor authentication (MFA) mechanisms to intercept authentication factors including smart card PINs, hardware token codes (RSA SecurID), SMS-based one-time passwords, and app-based push notifications. Interception methods include keylogging to capture smart card PINs or TOTP codes, SMS hijacking via SIM swapping or compromised messaging service providers, MFA prompt bombing (fatigue attacks sending repeated push notifications until the user approves), and adversary-in-the-middle (AiTM) phishing frameworks that relay credentials and capture session tokens post-MFA. Nation-state groups including Kimsuky (proprietary OTP interception tool), APT42 (cloned websites capturing MFA tokens), and Chimera (registering adversary phone numbers on compromised accounts) have employed these techniques. Criminal group LAPSUS$ operationalized MFA fatigue at scale against major technology firms, achieving access by sending repeated Authenticator push notifications until users approved out of confusion or frustration.
MITRE ATT&CK
- Tactic
- Credential Access
- Canonical reference
- https://attack.mitre.org/techniques/T1111/
Elastic Detection Query
sequence by azure.signinlogs.properties.user_principal_name with maxspan=30m
[any where event.dataset == "azure.signinlogs" and
event.outcome == "failure" and
azure.signinlogs.properties.authentication_requirement == "multiFactorAuthentication" and
azure.signinlogs.properties.authentication_details.authentication_method in
("PhoneAppNotification", "PhoneAppOTP", "OneWaySMS", "TwoWayVoiceMobile", "HardwareToken")] with runs=5
[any where event.dataset == "azure.signinlogs" and
event.outcome == "success" and
azure.signinlogs.properties.authentication_requirement == "multiFactorAuthentication"]Detects MFA fatigue (prompt bombing) attacks using Elastic EQL sequence with the 'with runs' syntax. Identifies users who accumulate 5 or more consecutive failed MFA authentication events within a 30-minute window, followed by a successful MFA sign-in. Targets Azure AD sign-in logs ingested via the Elastic Azure integration. The runs=5 clause on the failure event efficiently replaces the need for a separate aggregation step.
Data Sources
Required Tables
False Positives & Tuning
- Users in areas with poor cellular or internet connectivity who experience repeated push notification timeouts or SMS delivery failures before eventually succeeding on a stable connection
- IT helpdesk staff or identity administrators deliberately testing MFA enrollment, reset, or failover flows against active accounts during onboarding or incident response procedures
- Automated integration test suites or CI/CD pipelines that authenticate against MFA-enabled service accounts and include retry logic on transient failures
Other platforms for T1111
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1MFA Fatigue Simulation via Repeated MSAL Authentication Requests
Expected signal: Azure AD Sign-In Logs (AADSignInLogs): 10 entries for the test account — each with ResultType indicating MFA prompt sent or denied, AuthenticationRequirement=multiFactorAuthentication, AuthenticationMethodsUsed=PhoneAppNotification. Events appear within a 3-5 minute window, all from the same source IP (the test machine). If any prompt is approved, a success event (ResultType=0) also appears.
- Test 2Smart Card API Enumeration via Custom Process
Expected signal: Sysmon Event ID 1 (Process Create): scard_probe.exe spawned from powershell.exe with the compilation command in ParentCommandLine. Sysmon Event ID 7 (Image Load): scard_probe.exe loading C:\Windows\System32\winscard.dll — InitiatingProcessFileName=scard_probe.exe is not in the allowlist of expected winscard.dll callers. Sysmon Event ID 11 (File Create): scard_probe.exe written to %TEMP%.
- Test 3OTP Keylogger via Low-Level Keyboard Hook Installation
Expected signal: Sysmon Event ID 1 (Process Create): PowerShell with command line containing SetWindowsHookEx, WH_KEYBOARD_LL references — triggers on process create. Windows Security Event ID 4688 (if command-line audit enabled). PowerShell ScriptBlock Log Event ID 4104 captures the full hook installation code. Behavior-based EDR (CrowdStrike, Defender, SentinelOne) should generate a keyboard hook behavioral alert for the WH_KEYBOARD_LL hook type.
- Test 4Adversary MFA Phone Number Registration via Microsoft Graph API
Expected signal: Azure AD Audit Logs (AuditLogs table in Sentinel / azure:aad:audit in Splunk): OperationName='List user authentication methods' — the enumeration creates an audit event. If the write command is executed (in authorized lab only): OperationName='User registered security info' or 'Add user StrongAuthenticationMethod' with the new phone number value in TargetResources[0].modifiedProperties. Both events include the actor's IP address and UPN.
References (12)
- https://attack.mitre.org/techniques/T1111/
- https://sec.okta.com/scatterswine
- https://www.microsoft.com/security/blog/2022/03/22/dev-0537-criminal-actor-targeting-organizations-for-data-exfiltration-and-destruction/
- https://www.mandiant.com/resources/blog/apt42-charms-the-cyber-landscape
- https://learn.microsoft.com/en-us/entra/identity/authentication/how-to-mfa-number-match
- https://learn.microsoft.com/en-us/azure/active-directory/identity-protection/concept-identity-protection-risks
- https://learn.microsoft.com/en-us/azure/azure-monitor/reference/tables/aadsigninlogs
- https://learn.microsoft.com/en-us/azure/azure-monitor/reference/tables/auditlogs
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1111/T1111.md
- https://dl.mandiant.com/EE/assets/PDF_MTrends_2011.pdf
- https://www.nccgroup.com/uk/research-blog/chimera-unc2975-january-2021/
- https://docs.microsoft.com/en-us/graph/api/authentication-list-methods
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