The group claiming responsibility said they support the Occupy Boston movement.
Boston Police are warning some of their members that usernames and passwords were compromised.
The investigation into who hacked the system was widening and the F.B.I. was brought in to assist.
Police believe the radical element that calls themselves’ “Anonymous” has hacked into their system along with others across the country.
“Our internal computer system has been breached and I believe compromised,” said Tom Nee, President of the B.P.P.A.
The Boston Police Patrolman’s Association urgently told members to change their passwords after the rebel group posted their names and passwords online.
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The group claimed they took aim at the Boston Police for their unprovoked brutality.
In a statement “Anonymous” said, “…future acts of aggression against our movements will be met with a vengeance…”
“It’s outrageous and it’s not funny. We will pursue this to the fullest extent of the law,” said Tom Nee.
At the height of the demonstrations dozens of protestors were arrested and arraigned.
Some protestors said they did not want help from “Anonymous.”
“There was the one instance of police brutality, that does not mean all of them so you cannot go and target all of them,” said Shaunn Cartwright of Occupy Boston.
“I don’t see how actions like that would support the movement and I would encourage people to disassociate themselves with that because I think it’s wildly incongruent with the message of the movement,” said another protestor.
At Boston Police headquarters they said their website had not been breached but they encouraged all members to change their passwords.
Also on Saturday night, 21 acts of vandalism and graffiti were being investigated by Boston Police on buildings in downtown Boston.
Police believe the vandalism is linked to the Occupy Boston protests.
In Boston, only names and passwords were posted while in Birmingham, Alabama social security numbers were leaked onto a website for the public to see.