1. A method of analyzing messages in a computer system comprising: receiving a message including symbols at a computer, including a computer readable storage medium and processor, in the computer system; performing, by the computer, a lexical analysis of the message, the lexical analysis generating a sequence of tokens based on the symbols included in the message, wherein a token in the sequence of tokens corresponds to a category of symbols, and wherein the category of symbols corresponds to a plurality of symbols having different values; determining a message digest for the sequence of tokens, wherein the message digest is updated as each token in the sequence of tokens is identified during the lexical analysis; assigning the message to a cluster group based on the message digest.