USB ports are not intended to directly interface with simple circuitry, but only with fairly complicated USB transceivers as found inside of USB-enabled microcontrollers or peripheral chips.
However, you are just using the USB power lines. A small minority of systems / hubs permit software control of individual ports' power. If your system or hub has that capability you can possibly use that to turn the LED on and off. But you may have to look for quite a while to find a hub which actually has the pass transistors (even when hub ic's may have the pins to control such transistors, typically none actually get installed on the board).
For a portable project which does not require extremely careful selection of host hardware, you will have to use a USB-enabled microcontroller or interface chip.