A new report from the American Civil Liberties Union shows a dramatic increase in the U.S. Department of Justice’s electronic surveillance of Americans under the Obama administration.

Documents obtained by the ACLU through a Freedom of Information Act request revealed that under President Obama between 2009 and 2011, warrantless electronic surveillance requests by the Justice Department to spy on phone communications increased 60 percent from 23,535 to 37,616.

The number of people whose phone calls were subject to such surveillance during that same time period tripled.

Phone numbers called and received, emails sent and received, and other Internet communications were all monitored by the federal government via “pen register” and “trap and trace devices” — systems that measure the data, not the content, about the communication.

Such techniques are different from wiretaps, which monitor the content of communications.

More people were subjected to federal government pen register and trap and trace surveillance of their phones in the past two years than in the previous decade.

DOJ surveillance of Internet communications, while rarer, increased 361 percent between 2009 and 2011.

The ACLU’s report adds to a list of revelations over the past year about the U.S. government’s domestic surveillance efforts.

A recent Congressional inquiry, the first of its kind, revealed that cellphone carriers responded to 1.3 million demands from law enforcement in 2011, The New York Times reported in July. The requests included subscriber data such as text messages and location data.

Google’s transparency report revealed that the U.S. federal government led governments across the globe in requests for user information. In 2011 the U.S. government requested user data 12,271 times.

Google reported to its users that it complied 93 percent of the time last year.

Twitter’s transparency report revealed that the U.S. government requested user data from the company 679 times between January 1 and June 30 of this year.

The FBI also recently renewed its push for social networking sites to build in “back doors” for federal law enforcement’s use. The agency is becoming increasingly concerned that new online communications technologies will make it more difficult to intercept communications from targets of interest.

Additional information can be surmised about a person from a brief glance of a contact list alone, without exploring the content of the communications between individuals.

“If reviewing your social networking contacts is sufficient to determine your sexuality, as found in an MIT study a few years ago, think what law enforcement agents could learn about you by having real-time access to whom you email, text, and call,” wrote Naomi Gilens, Legal Assistant with the ACLU’s Speech, Privacy, and Technology Project.

Several former NSA officials with knowledge of the agency’s domestic spying efforts are also on record in a legal battle against the U.S. government to end its warrantless surveillance of Americans.

In August, however, a federal court ruled that citizens can only sue for damages after the government acts on information obtained improperly, and cannot win damages for the mere unlawful collection of information authorized by the Foreign Intelligence Surveillance Act.

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