In this article we present a steganographic system that permits the sending, reception and recuperation of secret data hidden in the TCP/IP packet header fields that are often unused or that exhibit some intrinsic redundancy to said protocols. The Mukul (meaning secret or hidden in the Mayan language) steganographic system is developed using freeware: the Libpcap and Libnet function libraries for programming the routines in C, and the Q library for the graphic interface. We also present the protocol implemented for the testing of the system and the obtained results.
