9. A method of filtering an electronic message to detect a particular format, comprising the steps of: decomposing the electronic message into a set of components according to a predetermined component size; determining an observed phi of the electronic message; determining a plain-text phi of the electronic message as a function of the component size; and comparing the observed phi to the plain-text phi to determine if the electronic message includes data in the particular format.
9. A method of filtering an electronic message to detect a particular format, comprising the steps of: decomposing the electronic message into a set of components according to a predetermined component size; determining an observed phi of the electronic message; determining a plain-text phi of the electronic message as a function of the component size; and comparing the observed phi to the plain-text phi to determine if the electronic message includes data in the particular format. 11. The method of claim 9, wherein the step of decomposing the message comprises the step of breaking the message into N-grams, wherein N equals the component size.