1. A computer-implemented method comprising: receiving one or more characteristics of a client requesting access to protected content, the protected content comprising data; determining, with at least one processor, 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; selecting, with at least one processor, first challenge characteristics or second challenge characteristics of a challenge/response test based on the risk profile; generating a challenge/response test based on the selected challenge characteristics, the generating comprising: 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 providing 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.
1. A computer-implemented method comprising: receiving one or more characteristics of a client requesting access to protected content, the protected content comprising data; determining, with at least one processor, 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; selecting, with at least one processor, first challenge characteristics or second challenge characteristics of a challenge/response test based on the risk profile; generating a challenge/response test based on the selected challenge characteristics, the generating comprising: 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 providing 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. 8. The computer-implemented method according to claim 1 , wherein the first challenge characteristics and second challenge characteristics each reflect a number of characters to include in the challenge/response test, and wherein the first challenge characteristics reflect a greater number of characters than the second challenge characteristics.