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T1621 Multi-Factor Authentication Request Generation

Adversaries may attempt to bypass multi-factor authentication (MFA) mechanisms and gain access to accounts by generating MFA requests sent to users.

Adversaries in possession of credentials to Valid Accounts may be unable to complete the login process if they lack access to the 2FA or MFA mechanisms required as an additional credential and security control. To circumvent this, adversaries may abuse the automatic generation of push notifications to MFA services such as Duo Push, Microsoft Authenticator, Okta, or similar services to have the user grant access to their account.

In some cases, adversaries may continuously repeat login attempts in order to bombard users with MFA push notifications, SMS messages, and phone calls, potentially resulting in the user finally accepting the authentication request in response to “MFA fatigue.”123

Item Value
ID T1621
Sub-techniques
Tactics TA0006
Platforms Azure AD, Google Workspace, IaaS, Linux, Office 365, SaaS, Windows, macOS
Version 1.0
Created 01 April 2022
Last Modified 04 April 2023

Procedure Examples

ID Name Description
G0016 APT29 APT29 has used repeated MFA requests to gain access to victim accounts.3
G1004 LAPSUS$ LAPSUS$ has spammed target users with MFA prompts in the hope that the legitimate user will grant necessary approval.5

Mitigations

ID Mitigation Description
M1036 Account Use Policies Enable account restrictions to prevent login attempts, and the subsequent 2FA/MFA service requests, from being initiated from suspicious locations or when the source of the login attempts do not match the location of the 2FA/MFA smart device. Use conditional access policies to block logins from non-compliant devices or from outside defined organization IP ranges.4
M1032 Multi-factor Authentication Implement more secure 2FA/MFA mechanisms in replacement of simple push or one-click 2FA/MFA options. For example, having users enter a one-time code provided by the login screen into the 2FA/MFA application or utilizing other out-of-band 2FA/MFA mechanisms (such as rotating code-based hardware tokens providing rotating codes that need an accompanying user pin) may be more secure. Furthermore, change default configurations and implement limits upon the maximum number of 2FA/MFA request prompts that can be sent to users in period of time.2
M1017 User Training Train users to only accept 2FA/MFA requests from login attempts they initiated, to review source location of the login attempt prompting the 2FA/MFA requests, and to report suspicious/unsolicited prompts.

Detection

ID Data Source Data Component
DS0015 Application Log Application Log Content
DS0028 Logon Session Logon Session Creation
DS0002 User Account User Account Authentication

References

  1. Catalin Cimpanu. (2021, December 9). Russian hackers bypass 2FA by annoying victims with repeated push notifications. Retrieved March 31, 2022. ↩

  2. Jessica Haworth. (2022, February 16). MFA fatigue attacks: Users tricked into allowing device access due to overload of push notifications. Retrieved March 31, 2022. ↩↩

  3. Luke Jenkins, Sarah Hawley, Parnian Najafi, Doug Bienstock. (2021, December 6). Suspected Russian Activity Targeting Government and Business Entities Around the Globe. Retrieved April 15, 2022. ↩↩

  4. Microsoft. (2022, December 14). Conditional Access templates. Retrieved February 21, 2023. ↩

  5. MSTIC, DART, M365 Defender. (2022, March 24). DEV-0537 Criminal Actor Targeting Organizations for Data Exfiltration and Destruction. Retrieved May 17, 2022. ↩