MFA Fatigue (aka MFA Bombing/Push Spam) is a social engineering attack where the attacker repeatedly triggers MFA push notifications until the victim approves one out of frustration or confusion.

The Uber Breach (September 2022):

• Attacker (Lapsus$ group) obtained an Uber contractor's credentials (likely from the dark web after a prior breach)
• Bombarded the contractor with MFA push notifications repeatedly
• Eventually contacted the victim on WhatsApp, posing as Uber IT support, saying they needed to approve the notification to stop the spam
• The contractor approved → attacker gained access to Uber's internal network

Why it works:

• Exploits human fatigue and annoyance rather than technical flaws
• MFA itself isn't broken — the human factor is the weak point
• Push-based MFA is particularly vulnerable (approve/deny is just a tap)

Defenses:

• Use number-matching MFA (user must type a code displayed on the login screen)
• Implement rate limiting on MFA prompts
• Use FIDO2/hardware keys instead of push notifications
• Train users to report unsolicited MFA prompts immediately

Go deeper:

• MFA fatigue attack (Wikipedia) — push-bombing, the Lapsus$ Uber breach, and the number-matching mitigation.