Brett_Tabke - 2:04 pm on Jan 11, 2011 (gmt 0)
Wilkins acknowledged that his initial tests were on an older version of reCAPTCHA, but since that time, he has conducted tests on the new images produced by the system and found them to be even weaker than the older ones. In one of his original tests on the system, his success rate was five in 200. When that test was run on the new reCAPTCHA, the rate was 23 in 100.
One weakness of CAPTCHA schemes, though is that they use words that can be found in a dictionary. This makes it easier for machines to crack the phrases because they have something to compare them to for errors.
In addition, reCAPTCHA uses a “one-off” system. That means a letter in a word can be incorrect, and it will still be accepted by the system.
So if the reCAPTCHA phrase contains the word “meat” and a Webster enters “peat,” his or her response will still be interpreted as a valid one.