1. A method for authenticating an access attempt, comprising: detecting an access attempt by a user device over a network; providing a challenge-response authentication over the network to the user device, wherein the challenge-response authentication includes a multi-focal-point image having a first image object associated with a first focal point in the multi-focal-point image, a second image object associated with a second focal point in the multi-focal-point image that is different from the first focal point, and depth information associated with the first image object and the second image object, and wherein the challenge-response authentication is configured to display the multi-focal-point image and use the depth information to change a focus of the multi-focal point image between the first focal point and the second focal point; receiving, in response to providing the challenge-response authentication, an authentication response from the user device over the network; and determining whether the authentication response includes an indication of or information about the first image object when the first focal point is focused or the second image object when the second focal point is focused.