She was a phreaker and early computer hacker during the late 1970s and early 1980s. A member of the so-called Cyberpunks. She met computer hacker Kevin Mitnick (also known as Condor) in 1980, and together with another hacker, Lewis de Payne (also known as Roscoe), formed a gang of phone phreaks. In The Hacker's Handbook, Headley is referred to as "one of the earliest of the present generation of hackers" and described as successfully hacking the US phone system as a 17-year-old in 1977.
On October 25th 1983, Headley testified in front of the Governmental Affairs oversight committee as to the technical capabilities and possible motivations of modern day hackers and phone phreaks