The explosive rise of Brain-Computer Interfaces (BCIs) is unleashing the era of Brain-Brain Interfaces (BBIs) and the Internet of Brains (IoB), enabling seamless neural exchanges that could transform healthcare, collaboration, and human potential, yet at the peril of unprecedented neural data breaches, signal hijacks, and cognitive hijacking. Motivated by these looming threats amid Neuralink’s 2025 milestone of $$27+$$ human implants, this paper dissects the cybersecurity chasm in BBIs, unveiling a novel four-layered IoB architecture, from volition to ultra-tech channels, and a pioneering multi-tiered defense framework fusing neuro-encryption, AI anomaly detection, and post-quantum cryptography. Our contributions are 1) a layered blueprint fortifying neural pathways, 2) defenses slashing known threats by 90% in simulations, 3) countermeasures against mind-hacking via AI-mitigated synchronization, and 4) blueprints for blockchain neural controls and quantum-resilient comms. By establishing a secure foundation for BBI-based IoB networks, this work provides an essential roadmap for researchers and practitioners aiming to safeguard neural interfaces against emerging cyber threats. This study is a crucial step toward ensuring the ethical, secure, and scalable deployment of IoB systems, bridging the gap between cutting-edge neuroscience and advanced cybersecurity. With the increasing integration of brain-based communication technologies, the proposed security model serves as a cornerstone for future innovations, protecting cognitive privacy and enabling trustworthy brain-to-brain interactions.