1. A computer-implemented method, comprising: selecting a plurality of N-grams from a second plurality of N-grams, wherein the second plurality of N-grams are associated with a range of values of N and the plurality of N-grams are associated with a sub-range of the range of values of N, wherein each of the second plurality of N-grams comprises a sequence of N bytes, where N is an integer; generating a statistical content classification model based on occurrences of the plurality of N-grams, if any, in a set of training documents and a set of validation documents; providing the statistical content classification model to content filters to classify content into one or more of a plurality of categories; searching for the plurality of N-grams in the set of training documents; computing a plurality of scores for each of the plurality of N-grams with respect to the plurality of categories; searching for the plurality of N-grams in the set of validation documents; and determining a threshold for each of the plurality of categories.