The invention concerns a method for identifying a protocol of a data stream exchanged between two entities of a telecommunication network, the processing method comprising the following steps: on receiving data of the data stream, grammatical parsing of said data stream in order to identify a protocol of the data stream; in the event of failure to identify the protocol of the data stream by grammatical parsing, consulting a signature engine mapping protocols with corresponding signatures, and sequentially applying signatures to the data flow in order to identify a data stream protocol.