But it was two recent events that propelled the members of Anonymous to act. Sources told ABCNEWS.com that they were initially intrigued by the publication of Andrew Morton's biography of Tom Cruise, which was highly critical of Scientology. That drew them to the Internet for more information where they came across the leak of several church videos on YouTube featuring Cruise's wildly enthusiastic praise of Scientology.
The church called the book "a bigoted, defamatory assault replete with lies" and subsequently it was not published in the United Kingdom and Australia for fear of libel lawsuits.
The Anonymous members were particularly offended, however, by the church's attempt to have the leaked videos removed from the Internet. The church claimed showing the videos was a copyright violation.
"Those heavy-handed attempts to censor the Web outraged members of Anonymous," said church critic Dave Touretzky, a research professor of computer science at Carnegie Mellon University. "A lot of these Anonymous members are young kids and weren't aware of the [church's] history. They became curious about Scientology when the Cruise videos hit YouTube and saw how the church was reacting."
In the middle of January, Anonymous sent a message to the church that included the threat, "We have therefore decided that your organization should be destroyed. … We shall proceed to expel you from the Internet and systematically dismantle the Church of Scientology."
The church claims that on Jan. 18, they received 241 harassing phone calls and death threats. On Jan. 22, it claimed that three churches received bomb threats. Three days later, Anonymous broadcast a video that included protesters break-dancing in front of Scientology facilities.
On Feb. 10 and March 15, thousands of Anonymous members protested against the church in cities around the world, including Dublin, Melbourne, Toronto, London and New York. Many of the protesters wore masks inspired by the V character from the movie, "V for Vendetta," who was an anarchist leader fighting to overthrow a totalitarian government.
True to their name, most of the protesters have remained anonymous. But two of them, 21-year-old James Farrell and Charles Hicks, were arrested in the Atlanta area March 15 outside the Georgia Church of Scientology in Dunwoody.
"They were arrested for screaming and cursing on a bullhorn, which is against our hazardous conditions ordinance," said Dekalb County spokeswoman Keisha Williams. "Three others were cited or ticketed for violating the same ordinance."
Farrell and Hicks could not be reached for comment.
At another Anonymous protest that day in Mountain View, Calif., protesters handed out fliers advertising a Web site called www.exscientologykids.com, where former church members complain about their experiences.
One of the Web site's founders is Jenna Miscavige Hill, the niece of current Scientology leader David Miscavige.
Church officials in Mountain View said they have contacted the local police in Mountain View to report several threatening phone calls.
"I believe they are domestic terrorists," said Scientology's public affairs director Matt Ward.
But one of the protesters disputed that said ex-Scientologist Bill Offermann, a 63-year-old painting contractor who attended the rally and is not a member of the group, although he communicates with its members.
"They seem to want to expose the truth rather than make far-fetched claims. ... With the power of the Internet, there is very little that the church can do to stop them."