Definition
Stealth VPN is a marketing umbrella for VPN modes that use obfuscation to disguise their traffic. The exact technique varies: some products use Stunnel-wrapped OpenVPN, some use XOR scrambling, some use proprietary obfuscation, some use Shadowsocks-derived protocols. Different providers brand the same general capability with different names: 'Stealth,' 'Camouflage,' 'NoBorders,' 'Obfuscated Servers,' 'Chameleon,' 'Scramble.'
When You Need It
Stealth modes are essential when ordinary VPN connections are blocked. This is routine in China, Iran, Russia, the UAE, Turkmenistan, Saudi Arabia, and a number of other countries. It is also useful on certain corporate or campus networks that block VPNs as policy, and on hotel Wi-Fi systems that monetize a captive portal by blocking alternatives. For users on open networks, stealth mode is unnecessary overhead.
Limits
No obfuscation is permanent. Networks employing serious DPI continuously update their detection. The strongest stealth implementations are the ones that are actively maintained and rapidly updated — a stealth feature that worked a year ago may be detectable today. For the most aggressive censorship environments, even reputable VPN providers may have intermittent reliability.