Type 1 authenticationrefers to “something you know,” such as a password, PIN, or passphrase. This is the most common and oldest form of authentication used in information systems.
Other authentication types include Type 2 (something you have, such as a smart card or token) and Type 3 (something you are, such as biometrics). Some models also define additional types, such as location-based or behavior-based authentication.
While easy to implement, Type 1 authentication is considered the weakest because secrets can be guessed, reused, stolen, or phished. For this reason, security best practices strongly recommend combining it with other authentication types using multi-factor authentication (MFA).
NIST and CIS guidelines consistently discourage reliance on single-factor, knowledge-based authentication for sensitive systems due to its susceptibility to compromise.