A method of controlling a packet stream generated by an application installed in a mobile terminal, the stream being intended to be sent by the terminal over a communications network managed by an operator. The method includes the following acts implemented in the terminal, for at least one packet generated by the application: obtaining a first packet having a first header and payload data; transmitting a request message to a security module installed in the terminal, the message including a parameter of the first header; receiving a response from the security module, which includes an instruction relating to transmission of a second packet, the response being based on the parameter and established according to a processing rule; preparing the second packet by modifying the first header into a second header, based on the instruction, the second packet including the second header and the payload data; and transmitting the second packet.