Cyberattacks on critical infrastructure have increased in recent years, posing a significant threat to the stability and security of the affected nations. In this presentation, TeamT5 will introduce TeleBoyi, a Chinese-nexus APT that has not been disclosed previously. Based on our research findings, TeleBoyi shows a strong preference for targeting critical infrastructure, with a particular focus on the telecommunication sectors. The group has been active since at least 2014 and is currently still active. Their scope of targeting extends across numerous countries worldwide, including APAC, Americas, and Europe. Our presentation will cover TeleBoyi’s Tactic Techniques and Procedures (TTPs) including their weapons. Moreover, we will discuss overlapping TTPs with other notorious APT groups. We believe the techniques and tactics disclosed in this presentation can help blue teams prevent, detect, and respond to Teleboyi's attacks more efficiently and effectively.