Activision Blizzard Thursday warned users of its Battle.net gaming portal that their personal data has been accessed by attackers. The company recommended that players in North America and beyond immediately change their passwords. “This week, our security team found an unauthorized and illegal access into our internal network here at Blizzard. We quickly took steps to close off this access and began working with law enforcement and security experts to investigate what happened,” said Blizzard president and co-founder Mike Morhaime in an “important security update” posted late Thursday to the site.