Germany’s Federal Office for Online Security discovered this particular security breach when it looked up the activities of a number of criminal botnets. While specifics of this particular discovery were not released (probably due to the sensitive nature of the investigation that they would not want to give too much of the game away to the mice that they’re trying to flush out), it also remains to be seen as to just which particular group, or groups, could be the ones responsible behind these stolen email information.
If you’re a German citizen and want to check out whether your email address happens to fall into this 16 million group, the German government has set up a website that allows you to type in your email address. Heavy traffic to this website, however, has resulted in it being inaccessible for long periods of time today.