
Your company implemented a couple of private branch exchanges (PBXs) connected through ISDN trunks for voice communication. As a system architect, you are designing a SIP-based system to incorporate VoIP and web conferencing. To prevent cooperating entities from exfiltrating data, which of the following infra system flaws should be verified and mitigated?
A. D channel
B. Side channel
C. Covert channel
D. Out-of-band overt channel