The hacker, who calls himself The Jester and goes by the name th3j35t3r on Twitter, said he was motivated to take down WikiLeaks for patriotic reasons. He also said his other targets include Web sites used by Al Qaeda and other terrorists groups for recruiting purposes.
"www.wikileaks.org--TANGO DOWN--for attempting to endanger the lives of our troops, 'other assets' & foreign relations," the hacker said in a message on Twitter. "PS for me personally WL is a sideshow target. I am more interested in the big jihad recruiting and training sites," he said, according to ABC News.
Speculation about the source of the attack had ranged from the U.S. government, to foreign regimes embarrassed by the information WikiLeaks disclosed to The New York Times, Der Spiegel, Le Monde, and other major newspapers.
Among other things, the documents revealed serious concerns within the U.S. diplomatic community about the resolve and trustworthiness of several key allies, including Afghanistan and Pakistan, in the war on terror.
They also disclosed Saudi Arabia's wish for a U.S. military strike against Iran, and painted unflattering pictures of Western leaders like German Chancellor Angela Merkel and Italian Prime Minister Silvio Berlusconi.
In the wake of the leak, the White House ordered a security clampdown.
The administration is telling agency heads to develop stricter criteria for determining which federal employees are given access to secured computer systems and networks that store classified data.
"Our national defense requires that sensitive information be maintained in confidence to protect our citizens, our democratic institutions, and our homeland," said Office of Management and Budget director Jacob Lew, in a letter to agency heads.
"Any failure by agencies to safeguard classified information pursuant to relevant laws, including but not limited to Executive Order 13526 … is unacceptable and will not be tolerated," wrote Lew. President Obama signed Executive Order 13526 on Dec. 29, 2009. It mandates that federal agencies undertake a broad series of steps to protect information.