Eight major U.S. technology companies are calling on President Barack Obama and Congress to enact new curbs on American surveillance programs they say have given the government too much power.The companies, in full-page newspaper ads Monday, said the spying “in many countries has tipped too far in favor of the state and away from the rights of the individual.” The technology firms said the surveillance “undermines the freedoms we all cherish. It’s time for change.” The companies that made the public appeal are some of the most prominent technology names in the world – Google, Apple, Microsoft, AOL, Facebook, Yahoo, Twitter and LinkedIn. They have been stung in recent months by revelations of the vast scope of U.S. surveillance revealed in the cache of documents leaked by former U.S. national security contractor Edward Snowden. He is now living in asylum in Russia, even as the U.S. seeks his extradition on espionage charges. Some of the documents showed that the National Security Agency has broken into the communication links that connect Google and Yahoo data centers around the world. But other documents showed Microsoft had worked with the government to thwart encryption mechanisms meant to secure users’ Internet privacy. The eight companies said in their open letter they are “focused on keeping users’ data secure…to prevent unauthorized surveillance on our networks.” They urged the U.S. to “ensure that government surveillance efforts are clearly restricted by law,” and “proportionate” to national security risks the government faces. Lawmakers in Congress have been considering various restrictions on the surveillance but have not yet acted.