I don't know why you were pinged, but I do know that it wasn't from PPRuNe.
We take privacy extremely seriously, and will not reveal the IP addresses of accessors unless legally compelled to do so.
You were probably pinged by a robot scanner, looking for an unprotected PC. I recommend you look at
http://grc.com and check out the "Shields up" links to see if you are vulnerable.
---PPD