Even though he knew she was a scammer, Ragan decided to play along a little more. The scammer then asked him to download a screensharing program called TeamViewer. It can allow other users to connect to your computer over the Internet. It has legitimate uses, but, in this case, the scammer wants to use it download malicious programs onto Ragan's computer.
Unfortunately for the scammer, Ragan disabled certain features on the program, so she could only see his screen but couldn't actually access files or control his keyboard or mouse. He also left a note that said "I am a security researcher, and you've been busted. But nice try! :-)" that she could see on the desktop before explaining that he's a security researcher and hanging up.
You can listen to the whole call right here:
Remember, Ragan is a security professional and knew how to keep his computer safe while toying with the scammer. If you receive a call like this, hang up immediately. Don't engage with the scammer and never download a program like TeamViewer that gives them access to your computer.