16. The non-transitory computer-readable storage medium of claim 15 , wherein at least one token of the sequence of tokens is not used to create the message digest.
15. The non-transitory computer-readable storage medium of claim 14 , further comprising: instructions that cause the data processor to determine that the cluster identifier is not associated with a cluster group; instructions that cause the data processor to establish a first cluster group associated with the cluster identifier; instructions that cause the data processor to assign the message to the first cluster group; instructions that cause the data processor to, after assigning the message to the first cluster group, receive a new message; instructions that cause the data processor to determine a second message digest for the new message; instructions that cause the data processor to determine that the message digest is the same as the second message digest; and instructions that cause the data processor to assign the new message to the first cluster group.