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The hactivists for a video trailer denigrating the Prophet Muhammad. The amateurish YouTube video made in the U.S. has sparked violent protests in the Middle East and other regions.

To participate in the hactivists' campaign, a supporter goes to one of two file-sharing sites and downloads a program written in a scripting language that runs in a web browser.

Once the program is running, a person only has to click on a "start attack" button to send continuous requests to the target's website. All of the traffic seen by FireEye has come from Web browsers, an indication that the attackers are not using a network of compromised machines, called a botnet. Such networks are also a popular method for launching distributed denial of service attacks, .

"The bad part about this attack is it's so simple," Mushtaq said. "They're not using any botnet. They're using browsers."