WASHINGTON, July 27 — She’s had some frightening moments during the past several years. As an undercover investigator, Rita Katz attended pro-Palestinian rallies and fund-raising events disguised as a Muslim woman in order to expose the links of American Islamic groups to foreign terrorist groups. At one conference, the Potomac resident relates in her recently published book, she was seated on the right side of the room, with the other women and children as is the custom at such events, when suddenly someone from the left side of the room screams, “You are not a Brother! Get out!” “I hear raised voices again,” Katz writes. “Someone shouts, ‘The insolence! Who do they think they are? The next one we find we’ll tear apart! No recording in this hall, everyone! We mean that!’ “My heart is beating fast, and I am sweating. I pray to God that my perspiration won’t cause the $5,000 digital camcorder and back-up voice-recorder [that she is wearing under her clothes] to malfunction and that nothing will go wrong. Putting myself in danger is one thing, but risking my baby [she is pregnant]… there’s too much at stake. If I’m discovered, I’ll never be able to do this again.” “It was scary, especially in small meetings,” Katz, author of Terrorist Hunter: The Extraordinary Story of a Woman Who Went Undercover to Infiltrate the Radical Islamic Groups Operating in America (HarperCollins), says in an interview. “I tried not to think about it. “My husband used to tell me it’s good that I’m scared because that will make me more alert.” One fear for Katz, who spent much of her childhood and years as a young adult living in Israel and often spoke a mixture of Hebrew and Arabic, was that she might blurt out some word in Hebrew. She considered giving up this dangerous work. “I wanted to be a normal woman,” says the author, who is the mother of four children. “But I thought ‘If I don’t do this, no one else will do.’ ” In May, Katz told her story on the CBS news magazine, 60 Minutes, but in disguise. She also wrote her book under the name “Anonymous” to protect herself and her family from retaliation from groups, whose hidden links to al-Qaeda, Hamas, Islamic Jihad and Hezbollah she has exposed. However, last month, two of the groups she discussed in her book and on TV — the Heritage Education Trust and the Safa Trust — sued her and revealed her name and the identity of the SITE (The Search for International Terrorist Entities) Institute that she heads. Because the lawsuit is pending, Katz is reluctant to talk about the case. But she does say “this attempt to silence her” will not prevent her from continuing her work. Katz has good credentials to be hunting terrorist-connected Muslim groups. She was born in 1963 in southern Iraq’s Basra into a wealthy Jewish family. She remembers a happy childhood amid a small, but tight-knit, Jewish community. Her world fell apart when her father, who was in the import-export business, was accused of spying for Israel and arrested shortly after the Saddam Hussein’s Ba’ath Party seized power in 1968. “I’ll never forget how he was taken away from us, that we wanted to kiss him, but they [the authorities] didn’t permit that,” she said. The family, all of whose property was confiscated by the state, moved to Baghdad to be near her father. He was publicly hanged in 1969. Two years later, her mother, fearing for her life, organized an escape for the whole family through northern Iraq into Iran, then still ruled by the shah. From there, the family made its way to Israel, where Katz grew up. After earning a degree in Middle Eastern studies from Tel Aviv University, Katz joined her mother in a business venture, manufacturing and selling clothes to the fervently Orthodox. Often, on business visits, she remembers changing her clothes in her car to garb more appropriate for the Orthodox community — a precursor to her future work undercover in the Muslim community in America. Katz says she resisted coming to live in the United States because of her Zionist views (“I believed that Jews belong in Israe.l”), despite her physician-husband’s opportunity to advance in his field by working here. But after Israeli Prime Minister Yitzhak Rabin was assassinated by an Israeli in 1995, she and her husband decided “to try a different life [in the U.S.],” she says. She attempted to be a stay-at-home mom after her arrival, but soon became bored. So about five years ago, Katz answered an ad and was hired by a Middle Eastern research institute. (Because of her lawsuit, she doesn’t want to reveal the institute’s name.) On her first day on the job — much of her work was to entail “administrative stuff and copying,” her new boss had told her — she started reading documents in English and Arabic about the Holy Land Foundation for Relief and Development. “I saw differences in the translations,” Katz recalls. “The Arabic list was longer, and I recognized that some organizations mentioned in Arabic and not in English were Hamas front organizations.” That realization propelled her to start doing research on that group, collecting Arabic documents and eventually going undercover. Her work, through her SITE Institute, which is funded by various federal agencies and private groups needing to know about radical Muslim groups operating in the U.S., has led to closures of organizations, deportations and ongoing investigations. She also has provided the media with information. Two of her victories have involved the White House. In 2000, Katz learned through a Holy Land Foundation newsletter that HLF had been approved to receive federal aid. “I freaked out,” she says. A call to the White House put an end to a situation in which “the U.S. government could have been [indirectly] funding Hamas.” In another case, Abdurahman al-Amoudi, who was considered a moderate, had access to the Clinton White House. The author recorded him at an event at which he said he supported Hamas and Hezbollah. The tape she sent to the media ended his intimate relations with that administration, she says. Katz says her book is a wake-up call for the American people. “I wrote the book because Islamic fundamentalism doesn’t only exist in Pakistan and Afghanistan,” she says. “It is here and if we don’t understand it, we can’t fight it.” Despite being subjected to virulent anti-Semitic and anti-Israel propaganda in her undercover work, Katz believes that most Muslims living in America are moderate. A small group of people, however, funded by the Saudi Arabians and others, are trying to radicalize them. Katz is convinced that they will be stopped, and that the U.S. will eventually triumph over international terrorism.