Verifier Impersonation Attack

March 5, 2025

Verifier Impersonation Attack

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A Verifier Impersonation Attack is a type of impersonation attack where a perpetrator pretends to be a legitimate authentication server (verifier). This tricks users into revealing their credentials and sensitive information. This can lead to identity theft, account takeover, and other security breaches. 

What it is

In a verifier impersonation attack, the attacker creates a fake authentication server (or impersonates a real one) to lure users into authenticating with it. This could involve creating a fake login page or sending a fake authentication request. 

How it works

  • The attacker might create a website or application that looks identical to a legitimate login portal. 
  • They might send an email or message that appears to be from a trusted source, asking the user to log in. 
  • The attacker might intercept legitimate authentication requests and redirect users to their fake server.

Why it’s dangerous

When users authenticate with a fake verifier, their credentials & sensitive information can be easily stolen, exploited by being reused to gain unauthorized access to the user’s accounts or other systems. 

Examples:
  • You receive an email from what appears to be your bank. It asks them to log in to update their account information. The email leads to a fake login page where the user enters their credentials, which are then stolen by the attacker. 
  • An attacker creates a website that looks like a popular social media login page. Users are tricked into logging in, and their credentials are captured. 

Best Practices

  • Verify the authenticity of the verifier

Always double-check the URL and other details of the authentication server to ensure it’s legitimate. 

Employ strong passwords, two-factor authentication, and other measures to make it harder for attackers to gain access. 

  • Be wary of suspicious emails and messages

Be careful when emails ask you to log in or provide sensitive information. 

  • Use phishing-resistant MFA
Choose MFA solutions that can prevent verifier impersonation attacks; respond only to valid authentication requests from trusted parties, according to Rublon. 

Definition

A scenario where the Attacker impersonates the Verifier in an authentication protocol, capturing information that is used to to masquerade as a Claimant to the real Verifier.
SOURCE: SP 800-63