Anonymous launched the attack after BART officials blocked wireless access to disrupt organization of a demonstration protesting the July 3 shooting death of a 45-year-old man by BART police, who said the victim was wielding a knife. Reuters

San Francisco's mass transit system prepared for renewed protests Monday, a day after hackers angry over attempts to thwart earlier protests broke into a website and posted company contact information for more than 2,000 customers.

The action by a hacker group known as Anonymous was the latest showdown between anarchists angry at perceived attempts to limit free speech and officials trying to control protests that grow out of social networking and have the potential to become violent.

Anonymous posted people's names, phone numbers, and street and email addresses on its own website, while also calling for a disruption of the Bay Area Rapid Transit's evening commute Monday.

BART officials said Sunday that they were working a strategy to try to block any efforts by protesters to try to disrupt the service. Spokesman Jim Allison said BART police will be staffing stations and trains and that the agency had already contacted San Francisco police.

The transit agency disabled the affected website, myBART.org, Sunday night after it also had been altered by apparent hackers who posted images of the so-called Guy Fawkes masks that anarchists have previously worn when showing up to physical protests.

The cyberattack came in response to the BART's decision to block wireless service in several of its San Francisco stations Thursday night as the agency aimed to thwart a planned protest over a fatal shooting by transit police. Officials said the protest had been designed to disrupt the evening commute.

"We are Anonymous, we are your citizens, we are the people, we do not tolerate oppression from any government agency," the hackers wrote on their own website. "BART has proved multiple times that they have no problem exploiting and abusing the people."

BART spokesman Jim Allison described myBART.org as a "satellite site" used for marketing purposes. It's operated by an outside company and sends BART alerts and other information to customers, Allison said.

The names and contact info published by Sunday came from a database of 55,000 subscribers, he said. He did not know if the group had obtained information from all the subscribers, he said, adding that no bank account or credit card information was listed.

Allison said that BART's main website was protected from attacks as well.

Violation of free speech?

BART's decision to shut down wireless access was criticized by many as heavy handed, and some raised questions about whether the move violated free speech.

The contretemps began Thursday night when BART officials blocked wireless access to disrupt organization of a demonstration protesting the July 3 shooting death by BART police who said the 45-year-old victim was wielding a knife.

Activists also remain upset by the 2009 death of Oscar Grant, an unarmed black passenger who was shot by a white officer on an Oakland train platform. The officer quit the force and was convicted of involuntary manslaughter after the shooting.

Facing backlash from civil rights advocates and one of its own board members, BART has defended the decision to block cellphone use, with Allison saying the cellphone disruptions were legal because the agency owns the property and infrastructure.

"I'm just shocked that they didn't think about the implications of this. We really don't have the right to be this type of censor," Lynette Sweet, who serves on BART's board of directors, said previously. "In my opinion, we've let the actions of a few people affect everybody. And that's not fair."

BART officials on Sunday were also working a strategy to try to block plans by protesters to try to disrupt service Monday.

"We have been planning for the protests that are said to be shaping up for tomorrow," Allison said. He did not provide specifics, but said BART police will be staffing stations and trains and that the agency had already contacted San Francisco police.

Laura Eichman was among those whose email and home phone number were published by the hackers Sunday.

Data breach 'completely unjustified': victim

"I think what they (the hackers) did was illegal and wrong. I work in IT myself, and I think that this was not ethical hacking. I think this was completely unjustified," Eichman said.

She said she doesn't blame BART and feels its action earlier in the week of blocking cellphone service was reasonable.

"It doesn't necessarily keep me from taking BART in the future but I will certainly have to review where I set up accounts and what kind of data I'm going to keep online," Eichman said.

Michael Beekman of San Francisco told the AP that he didn't approve of BART's move to cut cellphone service or the Anonymous posting.

"I'm not paranoid but i feel like it was an invasion of privacy," he said. "I thought I would never personally be involved in any of their (Anonymous') shenanigans."

The group Anonymous, according to its website, does "not tolerate oppression from any government agency," and it said it was releasing the User Info Database of MyBart.gov as one of many actions to come.

"We apologize to any citizen that has his information published, but you should go to BART and ask them why your information wasn't secure with them. Also do not worry probably the only information that will be abused from this database is that of BART employees," the statement said.