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Single Factor Authentication

Definition: Single factor authentication (SFA) is a verification process that relies on a singular credential, such as a password, for user identification before granting access to a system.

Single Factor Authentication (SFA) represents the most basic form of user verification. In cyber security, it’s essential to verify the identity of individuals attempting to access resources such as data, systems, or online accounts. SFA achieves this by requiring a single piece of evidence from the user. While it is straightforward and user-friendly, it is also the least secure method of authentication as it relies on a single piece of information that can be easily compromised.

The exclusive reliance on one authentication factor, such as a password, is what makes SFA less secure compared to Multi-Factor Authentication (MFA) systems, which require two or more independent credentials. With the rising sophistication of cyber threats, SFA has become less common for protecting sensitive or valuable information, with a clear preference for more secure authentication methods.

What are some examples of Single Factor Authentication?

The most common examples of Single Factor Authentication are:

  • Passwords
  • PINs
  • Passphrases
  • Security Questions

Key Characteristics:

  • Simplicity: SFA is simple to implement and use, often requiring minimal user education.
  • Speed: Due to its simplicity, it usually allows for quick access to services.
  • Low Security: It is considered less secure since it depends on a single piece of information.
  • Vulnerability: SFA is susceptible to various attacks, such as phishing, brute force, and social engineering.


  • Real-World Example: Accessing a personal email account using only a password is a form of Single Factor Authentication.
  • Hypothetical Scenario: A user logs into an online forum by entering only their chosen username and password, which constitutes Single Factor Authentication.

Related Terms:

  • Multi-Factor Authentication (MFA): A security system that requires more than one method of authentication from independent categories of credentials.
  • Two-Factor Authentication (2FA): A type of MFA that specifically utilises two distinct forms of identification before granting access.
  • Password: A string of characters used for user authentication to prove identity or access approval to gain access to a resource.

Learn better by watching a video? Here is a YouTube video from Tom Olzak explaining Single Factor Authentication.

What is the OWASP Top 10: Download our flash cards to find out.

Inside you will find a description of the most common web vulnerabilities.

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