4. The method of claim 3 , further comprising: determining that the cluster identifier is not associated with a cluster group; establishing a first cluster group associated with the cluster identifier; assigning the message to the first cluster group; after assigning the message to the first cluster group, receiving a new message; determining a second message digest for the new message; determining that the message digest is the same as the second message digest; and assigning the new message to the first cluster group.
5. The method of claim 4 , wherein at least one token of the sequence of tokens is not used to create the message digest.