Anonymous claims it will launch cyberattacks against banking and government websites on Tuesday.
The group is calling the planned attacks OperationUSA or OpUSA, saying in a message on pastebin.com that they are a response to social and political injustices.
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"Anonymous will make sure that's this May 7 will be a day to remember. On that day anonymous will start phase one of operation USA. America you have committed multiple war crimes in Iraq, Afghanistan, Pakistan, and recently you have committed war crimes in your own country," the hackers said last month in a statement. "We will now wipe you off the cybermap. Do not take this as a warning."
The Department of Homeland Security issued a confidential warning last week that the group, made up of mostly Middle East- and North African-based criminal hackers, was preparing to launch the cyberattacks Tuesday but said that the disruption could be limited, according to a report on the security blog Krebs on Security.
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OpUSA follows a campaign last month called OpIsrael, which threatened to wipe Israel off the cybermap but had little impact.
Though the damage Tuesday also will probably be limited and primarily consist of website defacement, it's a sign that the U.S. doesn't have a solution for dealing with hackers from other countries such as Iran, according to Dave Aitel, CEO of the security firm Immunity.
"There is definitely going to be some level of real danger hidden among all the noise and nonsense," Aitel said. "There is no law enforcement that can take place really that can tackle hackers coming out of Iran. We are going to have to come up with a policy of what we are going to do when this activity over the Internet cannot be reached."
The government agencies Anonymous listed include the FBI, NATO and the National Security Agency. It also named some big banks websites as targets, including Bank of America, Chase, Citi, Wells Fargo and Capital One.
"As much as the financial community has invested in security—and they have invested a lot of money, they don't need another round of [distributed denial of service] attacks. ... It doesn't take a whole lot of success to cause them financial damage," Aitel said.
Though many of the large institutions on Anonymous' hit list have security in place that can thwart serious damage from cyberattacks, some of the smaller financial companies could be vulnerable, Aitel said.
"Smaller banks listed, like Bank of Oklahoma and some credit unions, may not have the latest and greatest in security, so they could have more problems," Aitel said.
—By CNBC's Cadie Thompson. Follow her on Twitter @CadieThompson.