1. A method of providing a challenge response test associated with a computer resource, the method comprising: generating, using a processor, a challenge response test image comprising: providing a first substantially well-formed image, comprising a first masked image having a visible portion entirely composed of portions of a first well-formed image, and a first plurality of image elements; and providing at least one ill-formed image, each at least one ill-formed image comprising a second masked image comprising at least one first ill-formed portion.