or maybe even Levenshtein:

http://en.wikipedia.org/wiki/Levenshtein_distance

One of those pretty much gets the job done and is easy to implement as a class 😉

If I was a betting man, I would say they used the Jaro-Winkler distance metric

http://en.wikipedia.org/wiki/Jaro-Winkler

...if I was a betting man that is 😎