17. The system of claim 14 , wherein the first challenge characteristics and the second challenge characteristics each reflect timeout periods during which the client must provide a response to the challenge/response test, and the first challenge characteristics reflect a shorter timeout period than the second challenge characteristics.
14. A system comprising: a memory device that stores instructions; and at least one processor that executes the instructions and is configured to: receive one or more characteristics of a client requesting access to protected content, the protected content comprising data; determine a risk profile for the client based on the client characteristics, the risk profile reflecting a likelihood that the client is unauthorized to access the protected content; select first challenge characteristics or second challenge characteristics of a challenge/response test based on the risk profile; generate a challenge/response test based on the selected challenge characteristics by: determining a challenge phrase comprising a plurality of characters; and dividing the challenge phrase into at least two character subsets selected from the plurality of characters comprising the challenge phrase; and provide the at least two character subsets for consecutive display on the client at a predetermined frequency, wherein the first challenge characteristics and the second challenge characteristics each reflect distortion levels used to distort characters of the challenge/response test, and the first challenge characteristics reflect less character distortion than the second challenge characteristics.