About 100 public advocacy and other groups plan to stage what they hope will be a big rally in Washington D.C. to protest the the controversial National Security Agency surveillance programs disclosed by document-leaker Edward Snowden in June.

The "Rally Against Mass Surveillance" is scheduled for the weekend of October 26, the 12th anniversary of the signing U.S Patriot Act by former president George W. Bush.

Among those organizing the two-day event are the American Civil Liberties Union, the Electronic Frontier Foundation, Mozilla, Reddit, Free Press and Freedom Works.

Organizers said attendees can meet with elected officials to discuss their concerns over the surveillance programs still used by the National Security Agency and other U.S. intelligence groups.

The groups will also stage a rally with what they hope will be thousands of people from around the country. Organizers are expecting several musicians and lawmakers opposed to the spying activities to attend the rally.

The goal is to demonstrate deep, grassroots-level opposition to the NSA's data collection activities, said Josh Levy, Internet campaign director for Free Press, an advocacy group.

"The idea is to unite the activists, civil liberties advocates and everyone else who is feeling betrayed and wants to restore their faith in privacy under the Fourth Amendment," Levy said.

In June, Snowden leaked to reporters classified documents that revealed details about government spying activities, more than 550,000 people have signed a petition calling for the programs to be shut down, Levy said. "We want to make [Congress] aware of the voices of genuine outrage that exists on the ground," Levy noted.

Plans for the demonstration come as the Obama Administration and NSA continue to stoutly defend the need for the surveillance programs.

At a Senate hearing earlier this week, NSA director Keith Alexander said that the agency plans to collect all U.S. telephone records and essentially store them in a "lock box" from where records of interest can be retrieved and analyzed.

Even as calls are mounting for the NSA to scale down its collection of data on American citizens, Alexander and some lawmakers defended the collection as vital to national security interests.

Jaikumar Vijayan covers data security and privacy issues, financial services security and e-voting for Computerworld. Follow Jaikumar on Twitter at @jaivijayan, or subscribe to Jaikumar's RSS feed . His email address is jvijayan@computerworld.com.