Data security utilizing historical password data

A computer program product comprising:

• one or more computer readable storage media and program instructions stored on the one or more computer readable storage media, the program instructions comprising:
• program instructions to generate a list of authorized password hashes for a respective username by:
• identifying a first password included in a first failed login attempt of a first authentication session, wherein the first authentication session includes a successful login attempt subsequent to the first login attempt;
• generating a hash of the first password if the first failed login attempt;
• and
• adding the generated hash of the first password to the list of authorized password hashes;
• program instructions to receive authentication credentials input in an authentication session, the authentication credentials including a username and a password;
• program instructions to generate a hash of the password of the received authentication credentials;
• and
• in response to determining that the received authentication credentials are not valid, program instructions to determine whether the list of authorized password hashes includes the generated hash of the password associated with the username of the received authentication credentials.

A computer system comprising:

• one or more computer processors;
• one or more computer readable storage media;
• and
• program instructions stored on the computer readable storage media for execution by at least one of the one or more processors, the program instructions comprising:
• program instructions to generate a list of authorized password hashes for a respective username by:
• identifying a first password included in a first failed login attempt of a first authentication session, wherein the first authentication session includes a successful login attempt subsequent to the first login attempt;
• generating a hash of the first password if the first failed login attempt;
• and
• adding the generated hash of the first password to the list of authorized password hashes;
• program instructions to receive authentication credentials input in an authentication session, the authentication credentials including a username and a password;
• program instructions to generate a hash of the password of the received authentication credentials;
• and
• in response to determining that the received authentication credentials are not valid, program instructions to determine whether the list of authorized password hashes includes the generated hash of the password associated with the username of the received authentication credentials.