Abstract: The various embodiments enable the prevention of an automated computer routine from passing a challenge-response test. A processor may generate a first character string and create a first image comprising first characters based on the first character string, and may generate a second character string and create a second image comprising second characters based on the second character string. The processor may create a third image by superimposing the first image and the second image. The processor may associate at least one decoy code with the third image, the at least one decoy code based on character(s) within the third image that are likely to be detected by an automatic character recognition process. The processor may present the third image as a verification challenge, and may determine that the verification challenge is failed in response to receiving a verification challenge response that matches the decoy code.