The hackers’ message, delivered via YouTube by a man wearing a red tie and a Guy Fawkes mask, was as bold and risky as anything produced by the Zetas, Mexico’s most ruthless crime syndicate. But this time, the Zetas were the target. Connect With Us on Twitter Follow @nytimesworld for international breaking news and headlines. They had kidnapped a geek with backup — a respected member of the hackers collective known as Anonymous. “You have made a great mistake by taking one of us,” said the video’s masked figure. “Release him.” Or else, the message said, the names of government officials, taxi drivers and journalists who worked with the Zetas would be published online. The goal, they said, was the arrest of these suspected collaborators, but was there a possibility they might be killed by a rival cartel? Yes, said self-identified members of Anonymous, acknowledging the danger. Beyond that, might the hackers also be targeted? Were they afraid? “Of course,” said a blog post on Monday. Still, some hackers said, it was time for Netizens to fight back in a country where the news media have been cowed into submission, and where the justice system is often complicit in heinous crimes that regularly go unpunished.  “We believe it is high time to say enough to the terrible situation caused by the falsehood of the government and lack of scruples of people who do not care about the welfare of their fellow human beings,” they posted. Anonymous appears to already have the information on collaborators. A person with knowledge of its operations, who did not want to be named for fear of reprisals, said that online group conversations on Monday showed that the hackers have “a list of 100 or so of the major contacts of the Zetas.” It was not clear how they obtained the tally, or how accurate it was. And that appeared to be a major concern. A Facebook message on Sunday from one of the so-called hacktivists said there were indications that the Mexican government had tainted the Anonymous operation, known as OpCartel, “putting in doubt the quality of the information.” Whether Anonymous will publish what it has is unclear. The original YouTube message, uploaded on Oct. 6, said that Nov. 5 would be “a day to remember,” and the group has already provided a first strike. Last week, Anonymous defaced the Web site of a former Tabasco State prosecutor, Gustavo Rosario Torres, replacing his usual message with the image of jack-o’-lanterns and an announcement that Mr. Rosario “es Zeta.” But on Monday, in the wake of a security firm’s report highlighting the potential loss of life from naming names, there were more mixed messages. A steady stream of posts on Twitter referring to OpCartel revealed an intense debate over the benefits and costs of moving forward. On Twitter and in private e-mails — members of Mexico’s underground online media said — there appeared to be a widening gap between supporters and opponents of Anonymous’s mission. This may have been by design. The blog post announcing that OpCartel would continue emphasized that “anyone who is not properly protected should immediately and publicly disassociate themselves from this operation.” Several Twitter accounts that had been active on the topic fell silent. Several other members of Mexico’s online crime-reporting community said that OpCartel was causing internal strife, and that they had been asked by friends to stay away from anything having to do with the operation, even basic Twitter posts.   Fred Burton, a vice president at Stratfor, which published the report warning against the Anonymous plan, said that fears of reprisals were well founded. “Informants in that world are usually found dangling from a bridge or beheaded,” Mr. Burton said. Those identified by Anonymous would be vulnerable to rival gangs, he said, while the hackers and their supporters might also be targets. And because Mexico’s criminal groups have infiltrated Mexican law enforcement, which has access to sophisticated tracking software, anonymity online might not be enough protection. At least three people believed to have been online tipsters have been killed recently because of what their murderers described on public banners as snitching. Still, perhaps because of the danger — or perhaps because of the desperate need of many Mexicans for a sense of control as crime spirals — support for OpCartel continued to flow through the Web on Monday afternoon. Several Twitter users posted WikiLeaks cables with information about the Zetas. Others offered moral support. “You will never falter you will not fail, bring down the corruption,” wrote a user with the handle @fingers_digita. “PLZ be careful comrades, EXTREMELY dangerous,” wrote @AnonOWS, using the hash tag #justice for emphasis. Even those unsure about OpCartel said that it was significant as a citizen revolt. That was the core defense in the Anonymous blog post, which said a small task force was formed because “the voice of the people have clamored for help.” And according to some experts, regardless of whether OpCartel goes forward, the anger and outrage of Anonymous will be remembered, and channeled for another day. “This is not about a desire for information,” said Hector Amaya, a Mexican professor of Media Studies at the University of Virginia. “It’s about the need for a remedy.