Correct, the proper terminology is Spiegel Online (SPON) and "Der Spiegel". SPON is very popular among Germans and has been one of the best journalistic sources of Germany. It's also received the embassy cables last year:

https://en.wikipedia.org/wiki/United_States_diplomatic_cable...

with El Pais, Le Mond, The Guardin and NYT.

For this very story: It has received some new presentation slides in the recent days that it's currently publishing. The FAZ and other German newspapers are referencing SPON for this particular story. So for this story SPON is the first/primary source.