Dutch language news article:
http://webwereld.nl/nieuws/109461/hacker-kraakt-server-met-klantgegevens-kpn.html

Update:

KPN Hackers Interviewed By Dutch News Site Nu.nl: ‘KPN Servers Were Badly Secured, Badly Maintained. We Could Have Disconnected Internet Users’ 
http://vrritti.com/2012/02/09/kpn-hackers-interviewed-by-dutch-news-site-nu-nl-kpn-servers-were-badly-secured-badly-maintained/