Distinguishing human-generated input from programmatically-generated input

One or more tangible, non-transitory, machine-readable media storing instructions that when executed by one or more computers effectuate operations comprising:

• sending, via a first channel, to a client computing device, a challenge of a test to determine whether a human or a computer is generating input;
• receiving, via a second channel, a response to the challenge, wherein the second channel and the first channel are not both accessible to a client-application in which the response is input, and wherein the test includes an image recognition task by which the response is determined from the challenge;
• and
• determining whether a human or computer generated the response based on performance in the image recognition task indicated by the response, wherein:
• the challenge is a challenge of a CAPTCHA,
• the challenge specifies a geographic location,
• the first channel comprises a first port of the client computing device inaccessible to a web browser executing on the client computing device and accessible to a CAPTCHA-application executing on the client computing device, the CAPTCHA-application being configured to receive the challenge and present the challenge to the user outside of a webpage in which the response is to be entered,
• the client-application in which the response is input is a web browser executing on the client computing device, and
• the operations comprise:
• sending, via the second channel, to a second port of the client computing device the webpage in which the response is to be entered, the second port being different from the first port, wherein the webpage includes an image of a map to be rendered in the web browser;
• and
• after sending the webpage, receiving an identification of the geographic location in the map.