Group was accused of involvement in pro-piracy Operation Payback.
Four members of the hacking collective Anonymous have pled guilty to a misdemeanour charge of conspiring to intentionally damage a protected computer.
The defendants pled via phone to a federal court in Virginia, US, after district judge Liam O’Grady questioned why prosecutors were pushing for more serious punishments than had been handed out in a similar case in California.
O’Grady said: "You’ve still got a disparity issue, and it’s a serious one."
He added that some of the defendants had been living "under the gun" of the case for three years while otherwise having "impeccable characters", since the charges could have led to convictions involving a decade in prison.
"And from what I have seen right now, California got it right," he said. "And you ought to be thinking about it."
Phillip Simpson, Anthony Tadros, Thomas Bell and Geoffrey Commander were among thirteen indicted last October for alleged involvement in Operation Payback, a campaign which targeted film and record industry bodies during the winter of 2010 as part of political action in favour of piracy.
Two other defendants have already pled guilty to the same charges and another is set to change his plea in September. The last six defendants will be tried in October.