8. The apparatus according to claim 6 , wherein the plurality of pieces of target data are messages transmitted or received by a server connected to a computer, wherein the processor is configured to: acquire the plurality of messages transmitted or received by the server, and calculate a first ratio at which the plurality of acquired messages conform to the second pattern character string.
8. The apparatus according to claim 6 , wherein the plurality of pieces of target data are messages transmitted or received by a server connected to a computer, wherein the processor is configured to: acquire the plurality of messages transmitted or received by the server, and calculate a first ratio at which the plurality of acquired messages conform to the second pattern character string. 9. The apparatus according to claim 8 , wherein the processor is configured to: determine whether the second pattern character string is to be re-created, based on the calculated ratio, and extract the partial character string from one or plurality of messages conforming to the first pattern character string among the plurality of acquired messages when a determination is made that the second pattern character string is to be re-created.