With the advent of Software Defined Radios (SDRs) you can now listen to an HF receiver via the Internet. Fortunately, many people have made their SDRs available for public use and listed them on websites. To listen, all you need is an internet connection and a modern web browser. Most cover 1 Mhz to 30 Mhz.
Even better, there are now a host of "extensions" that allow you to use the received signals in a number of ways. One in particular uses "Time Delay of Arrival" (TDoA) to compare the same signal received at two or more SDRs in different locations. Using the clock from an attached GPS receiver at each location, the approximate location of the signal's transmitter can be determined.
It's a relatively complex process that has been made super simple. Read more about the process and find specific steps on how to located a signal here.