Received a cold call stating that they (who are they?) received notice I had a trojan and it was going to cause my computer to crash and that it had damaged my firewall so that my anti-virus was not longer working. When I questioned who they were (heavy Indian accent) they claimed they were a company (couldn't understand the name) and the caller was from South Africa. He wanted me to check my registration number to verify that he was legitimate by typing in a command "assoc" and looking for the 12 digit number he gave me. He gave me his email as email@example.com and a phone number 5005252818 as the cust service number. I put him off by saying I wanted to check this out on my own and I would contact him if I was satisfied he was on the level. Looks like I was correct in my suspicions.
Here's my advice to people who receive such calls:
1: Find out who is calling (ask them). If it is not your ISP, hang up. Your ISP could possibly tell that you have a virus problem, if they are scanning their network. Calls from elsewhere should be considered especially dubious.
2: If they say that they are your ISP, ask for a name, then tell them that you will call the ISP customer service number and ask for that person. This is the safe way of distinguishing bogus calls from real ones. -- AT&T Uverse; Zyxel NBG334W router (behind the 2wire gateway); openSuSE 12.2; firefox 17.0