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The ecosystem of censorship circumvention tools (CTs) re- mains one of the most opaque and least understood, overshad- owed by the precarious legal status around their usage and operation, and the risks facing those directly involved. Used by hundreds of millions of users across the most restricted networks, these tools circulate not through advertisements but word-of-mouth, distributed not through appstores but under- ground networks, and adopted not out of trust but from the sheer necessity for information access. This paper aims to elucidate the dynamics and challenges of the CT ecosystem, and the needs and priorities of its stake- holders. We perform the first multi-perspective study, sur- veying 12 leading CT providers that service upwards of 100 million users, combined with experiences from CT users in Russia and China. Beyond the commonly cited technical challenges and disruptions from censors, our study also high- lights funding constraints, usability issues, misconceptions, and misbehaving players, all of which similarly plague the CT ecosystem. Having the unique opportunity to survey these at-risk CT stakeholders, we outline key future priorities for those involved. We hope our work encourages further research to advance our understanding of this complex and uniquely challenged ecosystem. 

VPNs (Virtual Private Networks) have become an essential privacy-enhancing technology, particularly for at-risk users like dissidents, journalists, NGOs, and others vulnerable to targeted threats. While previous research investigating VPN security has focused on cryptographic strength or traffic leakages, there remains a gap in understanding how lower-level primitives fundamental to VPN operations, like connection tracking, might undermine the security and privacy that VPNs are intended to provide.In this paper, we examine the connection tracking frameworks used in common operating systems, identifying a novel exploit primitive that we refer to as the port shadow. We use the port shadow to build four attacks against VPNs that allow an attacker to intercept and redirect encrypted traffic, de-anonymize a VPN peer, or even portscan a VPN peer behind the VPN server. We build a formal model of modern connection tracking frameworks and identify that the root cause of the port shadow lies in five shared, limited resources. Through bounded model checking, we propose and verify six mitigations in terms of enforcing process isolation. We hope our work leads to more attention on the security aspects of lower-level systems and the implications of integrating them into security-critical applications.