The disclosed technology addresses the need in the art for a detecting an unauthorized participant in a multiparty conferencing session. A system is configured to join a conferencing session, obtain a roster for the conferencing session via a Session Initiation Protocol (SIP) channel, and generate a roster hash value based on the roster. The system may further receive a reference hash value from a key management server and compare the reference hash value with the roster hash value. The system may determine that the roster is invalid when the reference hash value does not match the roster hash value.