When Senator Joseph R. McCarthy held hearings in the 1950s to question witnesses about their supposed ties to communism, critics accused him of fomenting a Red Scare hysteria.
Decades later, the term Green Scare was used to describe a series of sweeping federal prosecutions of people involved in radical environmental and animal rights groups.
Now, perhaps, comes the Nerd Scare.
That is the phrase used by the National Lawyers Guild to describe a wave of subpoenas and indictments aimed at people thought to be members of activist hacker groups like Anonymous and LulzSec, which are known for waging cyberattacks against corporations including Sony, Amazon and Visa.
On Monday, the guild unveiled a Web site, www.anonlg.com, meant to help people or groups accused of hacking to find free legal representation. In July, the Federal Bureau of Investigation arrested more than a dozen suspected Anonymous members accused of using a tool called the low orbit ion cannon to carry out a denial of service attack against PayPal.
The attack took the company’s Web site off line for four days in December. It was carried out, according to members of Anonymous, in retaliation for PayPal’s refusal to process credit card payments to Wikileaks, a whistle-blowing organization that has made public hundreds of thousands of sensitive documents from the United States military and the State Department.
Law enforcement authorities say the electronic attacks have cost millions of dollars. But others have said that they caused little lasting harm and should be treated more like a political protest than a serious economic crime.
That view fits with the history of the lawyers guild, a national group that the F.B.I. has admitted to trying to disrupt with counterintelligence programs and warrantless searches from 1940 to 1975. Since the 1930s, members of the guild, which has headquarters in Manhattan, have represented a host of defendants tied to left-leaning causes. Clients have included producers and screenwriters who refused to testify before a House committee investigating communist infiltration, protesters at national political conventions and people accused of being environmental extremists.
“It became pretty clear to us that this was a new wave of activism, protesting the growth of corporations’ power,” the guild’s executive director, Heidi Boghosian, said, referring to the Anonymous attacks. “And it seemed to us that it would also be a new chapter in the Justice Department’s view.”
Ms. Boghosian said that she was concerned that those accused of hacking were facing harsher penalties than their alleged actions might otherwise warrant because the cyberattacks were aimed at prominent companies and were motivated by sympathy for Wikileaks and its founder, Julian Assange, whose publication of secret documents was condemned by the Obama administration.
An indictment unsealed last month in San Jose, Calif., where PayPal is situated, said that 14 Anonymous members used an open source computer program to bombard PayPal computers with messages, thus denying service to legitimate users. The defendants are charged with intentionally damaging protected computers, which carries a maximum penalty of 10 years in prison and a $250,000 fine, and with conspiracy, which carries up to an additional 5 years and $250,000 for each count.
The Justice Department has said that the investigation into Anonymous, which has involved more than 75 searches in at least 10 states, is continuing.
In the spring, as word of the investigation spread, the lawyers guild decided to help the hackers. The new Web site offers advice for those who are served with subpoenas or whose homes are raided and includes a phone number to call for help in finding a lawyer. It also has links to a primer on government monitoring by the Electronic Frontier Foundation called “Surveillance Self-Defense” and an illustrated pamphlet called “If an Agent Knocks” by the Center for Constitutional Rights.
Over the last several weeks, the guild has sent messages to members across the country asking for pro bono volunteers to represent accused Anonymous members. Among those who responded was Omar Figueroa, in Sebastopol, Calif., who said that he was looking forward to exploring issues of law and technology that had not yet been heavily litigated.
Mr. Figueroa, who said that he was representing one of those indicted but would not reveal the name of his client, said that he questioned whether it was fair to say that Anonymous members had hacked PayPal computers when they had never penetrated the network, only flooded it with messages.
“They are trying to accuse someone of breaking and entering, when all they have done is ring the doorbell,” Mr. Figueroa said, “albeit in an annoying fashion.”
A guild member in San Francisco, John Hamasaki, said that his client had been indicted, and he described the investigation into Anonymous as “the almighty power of the federal government cracking down on ordinary citizens in a situation where nobody was hurt.”
The client, Keith Downey, a 26-year-old carpenter in Jacksonville, Fla., declined to discuss the charges against him. But, he said, he was surprised by “the government putting all of these resources into something so minor” and added that he was still shaken by his arrest several weeks ago.
“I woke up and literally had an assault rifle in my face,” he said. “It was the last thing I expected on a random Tuesday morning.”