(Photo: TheWikiLeaksChannel, via Wikimedia Commons)

The leaders of Apple Inc., Google Inc., Microsoft Corp. and other major technology companies on Thursday marked the one-year anniversary of former National Security Agency contractor Edward Snowden’s leaks with a plea to the Senate: Pass legislation to reform government surveillance.

Tim Cook of Apple, Larry Page of Google and Satya Nadella of Microsoft were among nine tech CEOs who signed an open letter to senators, urging them to “ensure that U.S. surveillance efforts are clearly restricted by law, proportionate to the risks, transparent and subject to independent oversight.” The other chief executives on the letter were Tim Armstrong of AOL Inc., Dick Costolo of Twitter Inc., Drew Houston of Dropbox Inc., Marissa Mayer of Yahoo Inc., Jeff Weiner of LinkedIn Corp. and Mark Zuckerberg of Facebook Inc. All of the companies are members of the Reform Government Surveillance coalition, which was formed in December.

The CEOs said their businesses have taken steps to make their services more secure and their interactions with the government over user data more transparent. But these efforts aren’t enough, they noted.

The Senate should approve a version of the USA Freedom Act that would “help restore the confidence of Internet users here and around the world, while keeping citizens safe.” The bill, which cleared the House last month, is intended to rein in the NSA’s wide-ranging data collection activities revealed by Snowden and make the government’s surveillance efforts more transparent. The tech executives said they’re concerned that the measure would allow the bulk collection of customer data to continue and does little to improve transparency.

“It is in the best interest of the United States to resolve these issues,” the tech leaders said. “Confidence in the Internet, both in the U.S. and internationally, has been badly damaged over the last year. It is time for action.”

The USA Freedom Act and its Senate companion are pending in committee in the Senate. The Senate Intelligence Committee is holding a hearing Thursday afternoon to review the House bill.

Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., who introduced his chamber’s USA Freedom Act, said in a written statement that he will push for a “stronger” bill.

“All Senators should support real reform that bans bulk collection of data, provides greater accountability, and improves transparency,” he said. “I urge all Senators to join me in doing so.”