U.S. activists who thought Twitter was a secure way to communicate during demonstrations may have another thing coming. The New York District Attorney's Office has begun sending subpoenas to Twitter seeking data on protesters arrested during the Occupy Wall Street protests last year.

Late last week, activist Jeffrey Rae received one such email, which included a copy of a subpoena from the D.A. requesting data from his Twitter account. The letter, which has been published on Scribd, demands that Twitter hand over a list of data, including all public tweets from Rae's account between September 15 and October 31, 2011.

Other information sought by the D.A.'s office includes his name, address, records of session times, the length of those sessions, the types of devices used by Rae to access Twitter and any IP addresses from which he connected.

Rae was one of several hundred people who were arrested on October 1 for attempting to march across the Brooklyn Bridge as part of the ongoing Occupy Wall Street protests. Like others, he was charged with blocking traffic, improper use of a roadway and failure to obey orders.

Rae said he plans on challenging the subpoena in court. The District Attorney's Office did not respond to inquiries from ReadWriteWeb via telephone or email seeking comment.

This is not the first time Twitter has been asked to hand over data on Occupy Wall Street protestors. In February, activist Malcom Harris got a similar notice from Twitter'e legal department via email. Like Rae, Harris had his lawyer file a motion to challenge the subpoena.

"The biggest danger that comes from this subpoena isn't that it'll help convict me -- I don't think a judge will have any trouble understanding what happened on the bridge -- but that it will produce a chilling effect and discourage people from using Twitter while protesting" Harris wrote for Reuters. "It's a win-win for prosecutors: Either they use Twitter archives to build cases against demonstrators, or they scare us away from using the platform."

Storifying Wall Street: Social Media Fuels Unrest

The Occupy Wall Street protests and their offshoots across the country have largely died down since their peak in the late fall, although the movement is still active. Like other unrest throughout the world in the last few years, the anti-Wall Street demonstrations were both documented and partially fueled by social media tools. Just as in other parts of the world, Twitter in particular played an instrumental role in helping activists stay in touch and document what happened on the ground.

Authorities realize this and are hoping to pry some more information out of companies like Twitter. Since the subpoenas in these cases are not legally sealed, Twitter is free to notify its users of the requests, which it has a policy of doing.

Last year, similar requests were made by federal authorities as part of their ongoing case against Wikileaks. Privacy advocates were troubled when Google willingly may have handed over private Gmail data belonging to Jacob Appelbaum, a Tor developer and known Wikileaks supporter.

About a month later, a U.S. Federal Court ordered Twitter to grant the Justice Department access to private data about three Wikileaks supporters. As in Rae's case, the requested data included IP addresses and session times. A law called the Stored Communications Act allows authorities to seek data like this without a search warrant, a fact that does not sit well with civil libertarians and digital privacy advocates.

Twitter Subpoena