Senator Dianne Feinstein, chair of the Senate Select Committee on Intelligence, said recent "lone wolf" terrorism attacks show that propaganda from groups like Islamic State are inspiring attacks on U.S. soil.
"One of the problems is that the Internet as well as certain specific Muslim extremists are really firing up this lone wolf phenomenon.
"These attacks and the multiplicity of attacks in 2014 show that their propaganda is having some effect," the Californian Democrat said on CNN's "State of the Union" television program.