Exemplary methods and systems for verifying human interaction with a computer interface are described herein. An exemplary method includes a human-interaction verification system detecting a request by an access device to access network-based content, providing, for display by the access device, a visually dynamic representation of one or more security images associated with a passcode in response to the access request, receiving, by way of the access device, challenge-response input associated with the visually dynamic representation of the one or more security images, and performing an access operation based at least in part on a comparison of the challenge-response input to the passcode.