What is UniversalDVC and how does it create a tunnel over RDP?

UniversalDVC (UDVC) uses dynamic virtual channels (DVC) by registering a UDVC plugin DLL on the RDP client and running a server executable on the target. After registration via `regsvr32`, the plugin listens on a configurable local port (default 31337). The UDVC-Server connects to an internal service (e.g., HTTP on port 80), and the client can then access that internal service through its local port, effectively tunneling traffic through the RDP session.