A New Data-Hiding Approach for IP Telephony Applications with Silence Suppression

Even if information hiding can be used for licit purposes, it is in- creasingly exploited by malware to ex ltrate data or to coordinate a acks in a stealthy manner. erefore, investigating new methods for creating covert channels is fundamental to completely assess the security of the Internet. Since the popularity of the carrier plays a major role, this paper proposes to hide data within VoIP tra c. Speci cally, we exploit Voice Activity Detection (VAD), which sus- pends the transmission during speech pauses to reduce bandwidth requirements. To create the covert channel, our method transforms a VAD-activated VoIP stream into a non-VAD one. en, hidden information is injected into fake RTP packets generated during silence intervals. Results indicate that steganographically modi- ed VAD-activated VoIP streams o er a good trade-o between stealthiness and steganographic bandwidth.