1. A method for concealing information comprising a sequence of symbols, the method comprising the steps of: a concealing system, the concealing system comprising a network interface in communication with the internet and an encoder, obtaining location information from a web site indicated by a Uniform Resource Locator (URL); the concealing system obtaining via the internet rule information from a location indicated by the location information, the rule information being indicative of a rule for discarding a plurality of symbols; the concealing system using the rule information obtained to configure the encoder; and the encoder configured to form concealed information by applying to the information comprising the sequence of symbols at least one encoder rule determined by the configuration of the encoder; wherein the encoder comprises a symbol grouping module arranged to group symbols from the sequence of symbols into a plurality of groups of symbols and changing the sequence of the plurality of groups of symbols; and wherein the symbol grouping module is arranged to use the rule information to determine a number of symbols in each of the plurality of groups of symbols.