The Secure, Private Internet (SPIN) Research Group aims at making Internet communications secure and private. Towards this, we analyze the security and privacy provided by existing network protocols, tools, and services, based on which we propose design adjustments to regain users' security and privacy, or devise clean-slate Internet communication tools. Our work combines the development of practical systems with rigorous theoretical analysis and incorporates techniques from various disciplines such as computer networking, cryptography, and statistics. Particular problems we have explored in the past include Internet censorship resistance, network traffic analysis, network situational awareness, social network malware, mobile security, and multimedia information hiding.