An old news, as it started in September.  On 8 September 2012, Sendatsu published on the ownedcore a detailed study of the use of watermark within Blizzard’s World of Warcraft (WoW).  According to him, it seems that WoW adds an “invisible” watermark to screenshots (at least with JPEG in lower quality).   A capture of a screenshot without texture repeatedly produces a pattern similar to this one. 

The watermark carries 88 bytes with the account ID, a time stamp and the IP address of the server.  Clearly, it does not carry any personal information.   It seems that this Digimarc based watermark was in use since 2007 (when screenshots were added).

The aim of this watermark seems obvious to me.  There are many illegal WoW servers in the field.  Of course, users playing WoW through these non-Blizzard servers do not pay the monthly subscription.  This means a loss of revenue for Blizzard.  Finding the IP address of such unauthorized servers is a good start to fight piracy back .

Strangely, nobody reported a similar case for other Blizzard MMORPGs such as Diablo III or StarCraft.  Is it because nobody looked at, it yet? Or because there is no such watermark (less pirate servers)?

Update (30-oct-12):  The allegation that it is a Digimarc solution seems wrong.  Thus, currently no clue about the solution provider.