BERLIN, Jan. 6 (Xinhua) -- German authorities didn't know of a massive data leak that affected politicians until January, the Federal Office for Information Security (BSI) said on Saturday, quoted by German news agency DPA.
Early December, the agency was only aware of a data leak involving one person, not the hundreds of politicians who were affected in total, BSI said in a statement.
BSI said on Saturday that a member of parliament had informed the authority early December that there "had been questionable movements noticed on private and personal email and social media accounts".
BSI did not make the connection between this case and four more cases with the massive publication of personal data from politicians and celebrities until Jan. 4, according to DPA.
A spokesperson of German Chancellor Angela Merkel described the hacking attack as a "very, very serious incident".
The attack affected all political parties represented in the German parliament (Bundestag) except the far-right Alternative for Germany (AfD). Data records of politicians like Chancellor Merkel and German President Frank-Walter Steinmeier and also of journalists, musicians and television presenters have been posted online by the hackers.
According to German public broadcaster RBB, the stolen data had already been published last year via an anonymous Twitter account belonging to a platform whose operator is said to be based in Hamburg.
The published data included mobile phone numbers and addresses as well as very personal data like identity card numbers, credit card information, holiday pictures or internal documents of political parties.
German Justice Minister Katarina Barley said it was a "serious attack", adding that the perpetrators "want to damage confidence in our democracy and institutions".