Mozilla sent a cease-and-desist letter on Tuesday to a European company that created a piece of spyware masquerading itself as the Firefox browser. The move comes after computer security researchers said on Tuesday that they discovered that a well-known spyware program called FinSpy was spoofing Firefox. Mozilla was alerted by the researchers, who are with Citizen Lab, a research project that is part of the University of Toronto's Munk School of Global Affairs.