WikiLeaks, working with several major media outlets, begins publicly releasing over 250,000 diplomatic cables between the State Department and US embassies around the world. The cables date from 1966 to February 2010. None of the cables are classified at a level higher than “confidential,” the lowest classification level.
Clinton responds with the public comment, “This disclosure is not just an attack on America’s foreign policy interests, it is an attack on the international community: the alliances and partnerships, the conversations and negotiations that safeguard global security and advance economic prosperity. […] It puts people’s lives in danger, threatens our national security, and undermines our efforts to work with other countries to solve shared problems.” (USA Today, 11/29/2010) (The New York Times, 11/28/2010)
Mark Penn, Clinton’s chief strategist for her 2008 presidential campaign, sends Clinton an email in which he recommends, “I think you need to order a full scale review and upgrading of the cyber security of the State Department immediately.” (US Department of State, 9/30/2015)
However, despite this being the largest breach of State Department classified information in history, Clinton doesn’t change her personal communication methods, and continues to use an unsecured BlackBerry and an unsecured private email server. It is unknown if the State Department changes its cybersecurity as a whole, and if so, how.