The invention relates to a method, party challenging device (18) and computer program products for providing a challenge to a first terminal (10) intending to communicate with a second terminal (24) via two networks (N1, N2). The party challenging device receives a first electronic message (1M) concerning a transfer of media from the first terminal to the second terminal sent from the first terminal (10) and addressed to the second terminal (24), obtains communication contextual data associated with the first party or the first terminal, provides an electronic challenge message (CHM) including a challenge (CHl1) based on the obtained data and sends the challenge message to the first terminal in order to enable a decision to be made how to process the invitation message for the second terminal based on the correctness of a response (RM) including a response to the challenge.