Call supposedly from Microsoft Technical Support, to tell me that my computer was spewing out 'garbage' on the Internet. I didn't let them go any further, but the next part of their pitch is to tell you to go to a website and download their software to fix the problem.
DO NOT DO THAT!!! TELL THEM THAT THEY ARE CRIMINALS, TELL THEM NOT TO CALL AGAIN AND THEN HANG UP.
First, the caller isn't from Microsoft. Next, despite our suspicions, Microsoft doesn't have a way to tell what your computer does on the Internet. Then, the software they want you to download harvests every bit of information it can from your computer and transmits it to them, so they can resell it or commit identity fraud.