During her first research project, she suspected that the Holy Land Foundation, a charity organization dedicated to supporting humanitarian programs primarily in the West Bank and Gaza, was a front group for Hamas.
It analyzes "corporate records, tax forms, credit reports, video tapes, internet news group postings and owned websites, among other resources, for indicators of illicit activity".
[10] With the SITE Institute, which she co-founded to monitor Islamic extremist websites and to expose terrorist front groups, Katz worked with federal investigators in terrorism cases.
[12][13] Clarke wrote that she and Steven Emerson, for whom she formerly worked, regularly provided the White House with a stream of information about possible Al Qaeda activity inside the U.S. that was apparently largely unknown to the FBI before the 9/11 attacks.
[15] In May 2003, Katz published an anonymous semi-autobiography entitled Terrorist Hunter: The Extraordinary Story of a Woman Who Went Undercover to Infiltrate the Radical Islamic Groups Operating in America (Harper Collins, 2003; ISBN 9780060528195).
She appeared in disguise on the CBS newsmagazine, 60 Minutes, to promote her book using the pseudonym "Sarah", and wearing a wig and a fake nose,[16] to protect herself and her family from retaliation from groups that she said were linked to al-Qaeda, Hamas, Islamic Jihad, and Hezbollah.
Katz issued the video via a private link to a SITE web page to White House counsel Fred F. Fielding and Joel Bagnal, deputy assistant to the President for Homeland Security.
She said the premature disclosure tipped al-Qaeda to a security breach and destroyed a surveillance operation to intercept and pass along secret messages, videos and advance warnings of suicide bombings from the terrorist group's communications network.
Katz said she has been the victim of a smear campaign and of attempts to intimidate her, adding:"As they were never able to challenge the accuracy of my research, and as they were upset by the ramifications of it in terms of arrests, indictments, and raids, a few Muslim activist organizations have on occasion tried to portray me as a Muslim-basher.