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MITRE ATT&CK · T1621

Multi-Factor Authentication Request Generation

MITRE · cited in 10 of our lessons

Explanation

What attackers do. Attackers who already have a password trigger repeated MFA push notifications, calls or prompts until the user approves one by mistake or from fatigue. This serves the Credential Access tactic and is often called MFA fatigue or push bombing.

How to defend. Move to phishing-resistant MFA, or at least use number matching and show location and application context in prompts. Limit the number of MFA requests allowed in a period and alert on excess. Teach users to report unexpected prompts and to deny them, and treat such reports as a sign the password is compromised.

Signs to look for. Look for many MFA requests to one user in a short period, an approval following a burst of denials, and sign-ins from unusual locations right after approval. A common gap is not alerting on denied prompts at all.

Open the technique on MITRE ATT&CK
The official text
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. If adversaries lack credentials to victim accounts, they may also abuse automatic push notification generation when this option is configured for self-service password reset (SSPR). 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.”

© The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation (MITRE ATT&CK®).

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