Multiple-factor authentication

A computer-implemented method comprising:

• providing data communications services to a plurality of remotely-situated client entities and verifying a first authentication factor for a user, from among a plurality of users, of the data communications services;
• generating a data communication request that relates to the data communications services, that:
• includes a first portion specifying at least one target endpoint associated with the user, includes a second portion associated with or indicating a security code and further includes a set of instructions which:
• are specific to the user, specify how to communicate the security code for the user, and specify different security codes for different types of communications;
• transmitting the security code to the user according to the set of instructions;
• and
• verifying, via data communications circuitry linked to the data communications services, a second authentication factor associated with or for the user by comparing input from the user to the security code.

A storage device including instructions which, in response to being executed by computer circuitry, cause a method to be performed, the method comprising:

• providing data communications services to a plurality of remotely-situated client entities and verifying a first authentication factor for a user, from among a plurality of users, of the data communications services;
• generating a data communication request that relates to the data communications services, that includes a first portion specifying at least one target endpoint associated with the user, includes a second portion associated with or indicating a security code and further includes a set of instructions which:
• are specific to the user, specify how to communicate the security code for the user, and specify different security codes for different types of communications;
• transmitting the security code to the user according to the set of instructions;
• and
• verifying, via data communications circuitry linked to the data communications services, a second authentication factor associated with or for the user by comparing input from the user to the security code.