A man views a news stand displaying national newspapers, some carrying the story on WikiLeaks' release of classified U.S. State Department documents, at a newsagent in central London, Monday, Nov. 29, 2010. The online whistleblower WikiLeaks released classified U.S. diplomatic cables that reportedly raise concerns about unflattering assessments of world leaders and revelations about backstage U.S. diplomacy. (AP Photo/Sang Tan)
U.S. authorities are conducting an intensive criminal investigation into the release of thousands of classified U.S. documents by the whistleblowing website WikiLeaks to media outlets.
The White House also ordered tighter security on Monday to prevent leaks like Sunday's dump of 250,000 U.S. diplomatic cables that included candid assessments of world leaders and disclosures on issues such as Iran's nuclear and missile programs.
Here are some facts about WikiLeaks:
* WikiLeaks says it is a nonprofit organization funded by human rights campaigners, journalists and the general public. Launched in 2006, it promotes the leaking of information to fight government and corporate corruption.
* In October, WikiLeaks released 400,000 secret U.S. files on the Iraq war. The documents involved sensitive subjects including abuse of Iraqi prisoners in U.S. custody, Iraqi rights violations and civilian deaths.
* In July, it released tens of thousands of secret U.S. military documents about the war in Afghanistan, offering them first to The New York Times, Britain's Guardian newspaper and Germany's Der Spiegel.
* The Pentagon said the Afghan war documents leak -- one of the largest in U.S. military history -- had put U.S. troops and Afghan informers at risk.
* Under the heading "Afghan War Diary," the 91,000 documents collected from across the U.S. military in Afghanistan cover the war from 2004 to 2010, WikiLeaks said in a summary.
* Although founder Julian Assange has given few interviews recently, a website, www.wikileaks.org, and a Twitter feed, www.twitter.com/wikileaks, occasionally release material.
* Assange is an Australian who spends much of his time in Sweden. Earlier this year, he was accused of sexual misconduct by two Swedish women. Swedish prosecutors opened, then dropped, then re-opened an investigation into the allegations. Sweden has authorized a warrant for his arrest on suspicion of "rape, sexual molestation and unlawful coercion." But Assange has not been formally charged with any crime in Sweden, and he has denied all the accusations.
* Sweden's media laws are among the world's most protective for journalists. In addition, Sweden's Pirate Party, which advocates reform of copyright law, has agreed to host WikiLeaks' servers, giving it additional legal protection.
* WikiLeaks has no connection to the popular online encyclopedia Wikipedia.
(Writing by Eric Walsh, Doina Chiacu and Mark Hosenball in Washington; editing by Mohammad Zargham)