MFA Fatigue Attack: What Is It + Defense Techniques

Your employee in Berlin wakes up to 47 authentication requests on her phone. Exhausted and assuming it's a glitch, she taps "Approve" just to make them stop. An attacker just gained access to your systems.

This is an MFA fatigue attack, one of the fastest-growing threats facing distributed teams. When HR is managing device security without dedicated IT support, these attacks exploit the exact gaps attackers look for.

What is MFA fatigue?

MFA fatigue (also called push bombing or MFA exhaustion) is a social engineering attack where cybercriminals overwhelm users with repeated authentication requests until the victim approves one just to stop the notifications.

Here's how it works. An attacker gets someone's username and password through phishing, credential stuffing, or dark web purchases. When they try to log in using these stolen login credentials, your multi-factor authentication system sends an authentication request to verify the login attempt.

Instead of giving up when the user denies the request, the attacker keeps trying. They trigger dozens or hundreds of MFA push notifications, bombarding users with authentication requests at all hours. The goal: wear down the user until they approve a fraudulent MFA request, either by accident, frustration, or because they think something is broken.

The attack succeeds because it targets human behavior rather than technical vulnerabilities.

How MFA fatigue attacks work

MFA fatigue attacks follow a three-stage process that exploits gaps in both security systems and operational workflows.

Stage 1: Credential theft

Attackers obtain valid login credentials through phishing emails, purchasing stolen data from breaches, or social engineering campaigns. For distributed teams, employees across different time zones are less likely to verify suspicious activity with security teams immediately, making credential theft easier to execute undetected.

Stage 2: Repeated authentication attempts

Once attackers have valid credentials, they use automated tools to trigger continuous login attempts. Each attempt generates a new MFA push notification to the user's authenticator app or device. These requests can come in waves of dozens or hundreds, often timed for maximum impact like late at night when users are more likely to approve requests without thinking.

The strategy relies on persistence. Most MFA systems don't limit the number of authentication requests, meaning attackers can send unlimited MFA requests without being blocked.

Stage 3: User approval

Eventually, users give in. They approve the request because they're half-asleep, assume it's a system error, or believe clicking "approve" will stop the notifications. Once a user approves a fraudulent MFA request, the attacker gains access to systems, applications, and data, where they can move laterally, escalate privileges, or deploy ransomware.

Why distributed teams face higher risk

When your team spans multiple countries, MFA fatigue attacks become significantly more dangerous. The risk stems from operational gaps that attackers actively exploit.

Fragmented security visibility

HR teams managing IT for distributed workforces often lack real-time visibility into device security. When devices ship directly to employees in different countries, security policies may not be consistently enforced. An employee in São Paulo might receive a laptop with different configurations than someone in Warsaw, creating inconsistent protection.

Time zone exploitation

Attackers target hours when employees are least alert. Your employee in Singapore receives authentication requests at 2 AM. By the time your San Francisco security team starts work, the breach already happened. Without 24/7 monitoring, attacks often succeed before anyone notices.

Inconsistent onboarding

When HR manages device provisioning through multiple vendors, security implementation becomes inconsistent. Some employees get devices with strong authentication controls. Others receive equipment where MFA is configured as an afterthought. Attackers target newly onboarded employees who haven't established security habits.

Offboarding delays

The gap between when someone leaves and when access is fully revoked creates attack opportunities. If a former contractor still has an authenticator app installed or login credentials weren't immediately disabled, attackers can exploit that window. For distributed teams, coordinating access revocation across countries often takes longer than it should.

What MFA fatigue attacks cost your operations

The consequences extend far beyond the immediate security breach. For HR and operations teams managing distributed workforces, MFA fatigue attacks create cascading operational problems:

• Operational disruption: When an attack succeeds, HR must coordinate with IT to lock down compromised accounts across multiple countries. You're fielding employee questions about device security, resetting credentials, and determining breach scope. For small teams, this response work can consume days of productivity.
• Compliance exposure: Distributed teams operate under multiple regulatory frameworks. GDPR, data protection laws, and industry regulations all require demonstrating appropriate security controls. An MFA fatigue attack exposes gaps in your access management systems that you'll need to explain during audits.
• Device security costs: After an attack, you often need to wipe and reconfigure compromised devices. For distributed teams, this means coordinating device returns, arranging temporary equipment, and managing logistics across countries. The costs add up: shipping, storage, replacement, and productivity loss.
• Employee trust erosion: When security systems fail visibly, employees lose confidence. They question whether other measures are adequate and whether the company takes security seriously. For distributed teams where trust is harder to build, this erosion creates lasting problems.

Five practical defenses against MFA fatigue

Protecting distributed teams requires controls that work across countries without creating friction for legitimate users.

Implement number matching for push notifications

Number matching adds verification to authentication requests. Instead of just tapping "approve," users must enter a specific code displayed on the login screen into their authenticator app. This makes MFA fatigue attacks dramatically harder because attackers can't provide the matching number.

Make this mandatory, not optional. Configure your authentication methods to require number matching for all push-based MFA requests. Most modern authenticator apps support this natively.

Set strict rate limiting on authentication attempts

Your MFA system should enforce hard limits on authentication requests within a specific timeframe. A reasonable configuration might allow three MFA requests within 15 minutes before requiring additional context or temporarily blocking further attempts.

Rate limiting prevents the core tactic: overwhelming users with dozens of rapid-fire authentication requests. When attackers can only trigger a few requests before being throttled, the attack becomes much less effective. Ensure these limits apply globally across all login endpoints.

Deploy risk-based authentication policies

Risk-based authentication evaluates additional context before sending MFA push notifications: device trust status, geographic location, network characteristics, and historical login patterns.

When an employee in London logs in from their managed laptop during business hours, that's low risk. But if someone attempts login from an unmanaged device in a country where you have no employees, at 3 AM, the system should require additional verification or block the attempt.

For distributed teams, risk-based policies reduce friction for legitimate users while making attacks harder. Employees don't get authentication requests while sleeping, but attackers trying to log in at odd hours trigger enhanced security.

Enable automated threat detection and response

Configure systems to detect MFA fatigue patterns: repeated failed authentication attempts, multiple MFA requests to the same user, and authentication attempts from suspicious locations.

When detected, automated responses should lock the affected account, notify your security team, and alert the user through email or Slack. For distributed teams without 24/7 security, automated incident response closes the gap between attack start and investigation.

Conduct regular security awareness training

Employees need to understand what MFA fatigue attacks look like. Training should be specific: if you get an MFA push notification and you didn't try to log in, deny it and report it immediately.

For distributed teams, training needs to account for language differences, time zones, and varying technical expertise. Make guidance actionable and give employees a clear reporting process.

Close security gaps with Deel's unified IT management

MFA fatigue attacks succeed when there are gaps between security tools, device management, and operational processes. For distributed teams, these gaps multiply when coordinating multiple vendors across countries.

Deel IT eliminates these gaps through unified device lifecycle management in 130+ countries:

• Pre-configured security from day one: Laptops arrive with security policies, authentication requirements, and access controls already in place. No window where devices are unprotected or setup depends on employee actions.
• Unified policy enforcement: Manage endpoint security across every device from one dashboard. Enforce consistent MFA requirements, monitor authentication attempts, and respond to incidents without juggling separate tools.
• Automated offboarding: Access revocation happens instantly through the offboarding workflow. Device access, credentials, and authentication tokens are all invalidated the moment HR marks someone as offboarded.
• 24/7 global support: IT support across 130+ countries means employees can immediately verify suspicious authentication requests and get help, regardless of time zone. This eliminates the vulnerability windows attackers exploit.
• Complete visibility: See which devices have MFA configured, identify authentication patterns indicating attacks, and respond before incidents escalate. Everything in one platform means no blind spots.

For HR and People Ops, this means you're not coordinating security across multiple vendors. Device security, authentication policies, and incident response are handled through one partner, which means fewer gaps and less complexity.

Book a demo to see how Deel IT strengthens authentication security across your distributed workforce.