Specifically the CH340 or FTDI USB-to-Serial drivers.
Once the driver establishes connectivity, the user must download the diagnostic software. The KKL 409.1 is most famously associated with the "VAG-COM" software, specifically the shareware versions (such as versions 311, 409, or the VCDS-Lite). It is important to note that while the cable is a hardware clone of the official interface, it generally only functions with the older, shareware versions of the Ross-Tech software or third-party freeware. Modern versions of the official VCDS software are encrypted to work only with genuine Ross-Tech hardware. Therefore, downloading the correct legacy software version is a requirement to unlock the cable's potential. kkl 409.1 software download
Most high-quality cables use this. Download the latest "VCP" (Virtual COM Port) drivers directly from CH340 Chipset: Specifically the CH340 or FTDI USB-to-Serial drivers