Russell Tice, a longtime insider at the National Security Agency, is now a whistleblower the agency would like to keep quiet.
For 20 years, Tice worked in the shadows as he helped the United States spy on other people's conversations around the world.
"I specialized in what's called special access programs," Tice said of his job. "We called them 'black world' programs and operations."
But now, Tice tells ABC News that some of those secret "black world" operations run by the NSA were operated in ways that he believes violated the law. He is prepared to tell Congress all he knows about the alleged wrongdoing in these programs run by the Defense Department and the NSA in the post-9/11 efforts to go after terrorists.
"The mentality was we need to get these guys, and we're going to do whatever it takes to get them," he said.
Tice says the technology exists to track and sort through every domestic and international phone call as they are switched through centers, such as one in New York, and to search for key words or phrases that a terrorist might use.
"If you picked the word 'jihad' out of a conversation," Tice said, "the technology exists that you focus in on that conversation, and you pull it out of the system for processing."
According to Tice, intelligence analysts use the information to develop graphs that resemble spiderwebs linking one suspect's phone number to hundreds or even thousands more.
President Bush has admitted that he gave orders that allowed the NSA to eavesdrop on a small number of Americans without the usual requisite warrants.
But Tice disagrees. He says the number of Americans subject to eavesdropping by the NSA could be in the millions if the full range of secret NSA programs is used.
"That would mean for most Americans that if they conducted, or you know, placed an overseas communication, more than likely they were sucked into that vacuum," Tice said.
The same day The New York Times broke the story of the NSA eavesdropping without warrants, Tice surfaced as a whistleblower in the agency. He told ABC News that he was a source for the Times' reporters. But Tice maintains that his conscience is clear.
"As far as I'm concerned, as long as I don't say anything that's classified, I'm not worried," he said. "We need to clean up the intelligence community. We've had abuses, and they need to be addressed."
The NSA revoked Tice's security clearance in May of last year based on what it called psychological concerns and later dismissed him. Tice calls that bunk and says that's the way the NSA deals with troublemakers and whistleblowers. Today the NSA said it had "no information to provide."
ABC News' Vic Walter and Avni Patel contributed to this report.