Three-quarters of post 9/11 plots targeting the United States at home and abroad are associated with radical Islamists, a new study finds.

The study, which analyzes 176 failed terrorist plots against U.S. targets, was conducted by Erik J. Dahl, a professor at the Naval Postgraduate School in Monterey, Cal., in conjunction with the Study of Terrorism and Responses to Terrorism (START) program at the University of Maryland.

The remaining 25 percent, according to the paper, are plots by right wing, anti-government groups.

The study concludes that many plots have been successfully prevented because of basic law enforcement efforts and increased intelligence collection. It finds that 45 jihadist plots against U.S. soil since 9/11 were foiled by the work of law enforcement authorities.

"When it comes to domestic attacks and securing the homeland," Dahl told Daily Beast contributor John Avlon, "what works is really good, old-fashioned policing-law enforcement, tips from the public, police informants – and not so much spies overseas or satellites run by three-letter government agencies."

But Dahl said that the government's success in foiling terrorist plots doesn't mean the United States can rest easy. "Everyone in American national security is amazed that we haven't had another 9/11 within America since 9/11," he said. "That's the good news."

"But the bad news," he told Avlon, "is that we do see this continuing, steady drumbeat of smaller-scale plots and attempted terrorist attacks. So the threat is definitely not gone."

In the days leading up to the 10-year anniversary of 9/11, U.S. officials have said they are particularly worried about smaller-scale, lone wolf attacks.

"We are concerned about the lone actors that are out there, we are concerned that al Qaeda or others may try to take advantage of the 9/11 anniversary events," White House terrorism advisor John Brennan said Wednesday.

President Obama agreed. "The risk that we're especially concerned over right now is the lone wolf terrorist, somebody with a single weapon being able to carry out wide-scale massacres…" the President said in an interview with CNN.

Reports surfaced Thursday that authorities had been alerted to a "credible" but unconfirmed three-person 9/11 anniversary plot targeting Washington, D.C. and N.Y. The plot appears to break the lone wolf trend. U.S. officials are now saying that al-Qaida chief Ayman al-Zawahiri initiated the plot.