The first time, I asked which IP address the DOS was coming from. They gave me a 192.168.x.x address (which is, of course impossible), but I pretended to be looking it up in the router for 5 minutes to keep them on the line. Of course, I told him there was no computer with that address here. After wasting 5 minutes of his time, I told him there weren't any PCs here. That actually didn't stop him, he switched to a Mac script. Then I asked if the DOS was IP or TCP and he said neither. So I said that proved he didn't know what he was talking about; so, he put on his supervisor. After yanking the supervisor around with technical questions he couldn't answer (but tried to), I revealed that I knew it was a scam and was intentionally trying to waste his time. I also mentioned that he was an idiot who didn't know what he was talking about (with the other scammer listening in, no doubt). Who knew that Indians know so many English swear words (which actually might mean they aren't really in India).
That does get one put on their do not call list