Inside VPN Mechanics: Encryption, Tunneling, and Privacy Limits
The article explains how VPNs encapsulate and encrypt packets, then route them through a tunnel to a server where encryption ends and normal routing resumes. It cites internet-wide scanning that found 9.8 million VPN servers and notes that some protocols, especially SSTP, had serious TLS downgrade vulnerabilities. The piece also highlights that VPNs do not hide everything, pointing to browser fingerprinting and cases where Android VPN apps failed to encrypt traffic or tunnel IPv6 and DNS.
A global scan identified 9.8 million VPN servers using OpenVPN, SSTP, PPTP, or IPsec. SSTP was especially weak: over 90% of discovered servers could be attacked via TLS downgrade. WireGuard, by contrast, implements a complete tunnel in under 4,000 lines of Linux code, using Curve25519 and ChaCha20Poly1305.
Research on Android VPN apps found 18% used tunneling without encryption, while about 84% ignored IPv6 and 66% ignored DNS inside the tunnel. Browser fingerprinting added another limit: Panopticlick data showed at least 18.1 bits of entropy, meaning only one in 286,777 browsers was expected to match another.
These findings could affect remote workers, privacy-focused users, and organizations that rely on VPNs for secure access. If some apps fail to encrypt, tunnel IPv6, or handle DNS, users may believe they are protected when they are not. The SSTP downgrade issue may push providers toward stronger protocols, while fingerprinting research may temper expectations that a VPN alone guarantees anonymity. Regulators and app stores could face pressure to improve disclosure, though the actual impact depends on adoption and enforcement.