XM Satellite Radio (XM) is a satellite radio (SDARS) service operated by Sirius XM Radio in the United States and Canada.
XM Radio Online (XMRO), XM's Internet radio product, offers many of XM's music stations and can be accessed from any Internet connected Windows or Macintosh computer, or via the iPhone/iPod Touch SIRIUS XM app.
This SonicWALL signature identifies legitimate XM Radio Online traffic.