The hackers, part of a group that gained notoriety for frequent cyber-battles with U.S. authorities, each pleaded guilty via telephone to one misdemeanor charge of conspiring to intentionally cause damage to a protected computer.
The charge carries a maximum of one year in prison and a fine of $100,000.
The four men along with nine others had been charged last October by the U.S. Attorney's office in the Eastern District of Virginia with a felony crime under which they could have faced a decade in prison.
Similar cases brought by the U.S. Attorney's office in San Jose were largely resolved through misdemeanor convictions with no jail time, and the federal judge overseeing the Virginia set of cases had asked why similar defendants were facing more severe punishment in his state.
"You've still got a disparity issue, and it's a serious one," U.S. District Judge Liam O'Grady told federal prosecutors on the case at a May hearing, according to a transcript of the proceedings.
Some of the defendants "have lived for the last three years under the gun of this investigation who otherwise have impeccable characters," O'Grady continued. "And from what I have seen right now, California got it right. And you ought to be thinking about it."
On Tuesday the four men - Phillip Simpson, Anthony Tadros, Thomas Bell and Geoffrey Commander - were allowed to call in their pleas to federal court in Virginia because the charge was a misdemeanor offense, O'Grady said.
O'Grady said it was the first plea he had handled by telephone.
Two other defendants in the case have already pleaded guilty to the same misdemeanor charge, and one more defendant is scheduled to change his plea in September. Six other suspected Anonymous hackers charged in the case are scheduled to go to trial in October.
A representative of the U.S. Attorney's office declined to comment on the case.
The change in the approach comes as the U.S. Justice Department has faced some criticism for aggressively pursuing a range of cyber cases, including pushing for lengthy prison terms even in instances when hackers had not profited from the conduct.
Internet activist Aaron Swartz committed suicide last year before going to trial for allegedly stealing millions of academic articles from a private database, a death Swartz' family blamed on "overzealous" prosecutors.
"There is a question of proportionality, in whether it makes sense to equate" crimes driven by political motivations as opposed to those motivated by greed and profit, said Hanni Fakhoury, a lawyer with the Electronic Frontier Foundation.
If protesters chain themselves to fences or trespass on private property, they may get citations or face misdemeanor charges, but rarely face felony convictions, said Fakhoury, who has counseled cybercrime defendants.
In testimony earlier this month before a House panel, the head of the Justice Department's criminal division, Leslie Caldwell, said prosecutors have been working hard to combat the threat of cybercrime. She said such activity has "increased dramatically over the last decade and caused enormous financial damage and innumerable invasions of Americans' privacy."
The Virginia case was over Anonymous' "Operation Payback," a group of 2010 attacks on music and movie industry websites allegedly launched in retaliation for the shutdown of file-sharing websites.
They used what are known as denial-of-service attacks to overwhelm websites and make them inaccessible, according to court documents.
The operation caused $8.9 million in damage and losses, prosecutors said. Three of the four men who pleaded guilty on Tuesday are under 30. The fourth, Commander, is 66.
The loose-knit international group has been in frequent battle with U.S. authorities not only over file-sharing but also other ideological causes such as the willingness of financial institutions to process donations for the anti-secrecy group WikiLeaks.
In March 2012, U.S. prosecutors in New York charged six suspected leaders of Anonymous for wreaking havoc on government and corporate websites.
One was sentenced last November to 10 years in prison for cyber- attacks on government agencies and businesses, including a global intelligence company. Another leading member who had been cooperating with authorities and was said to have helped disrupt more than 300 attacks was sentenced in May to time served.
© Thomson Reuters 2014