Who called from 4151112000

I have received a call from this number four days in a row. My caller ID says Name Not Known so I let it go to voice mail. As soon as the machine picks up, they hang up. Knowing this is a scam, I may try answering with "County Attorney" response. That should end the calls.

415-111-2000 called July 9, 2014 at 4:36 pm.  Caller ID = NAME NOT FOUND (means ATT can't find source of this call, which is a warning of SPAM).
Thank you 800notes, we see this spammer is fake MICROSOFT call to gather personal info and infest your computer. NO THANKS!!!!
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BLOCKED because:
1) they been calling many others on 800notes,
2) left no message
3) have caller ID of NAME NOT FOUND

dials and hangs up

I got a call from this number about 2 minutes after my computer did an automatic reboot. The call indicated there was a problem with my computer. Scary, they must be monitoring the computer, scary

They called me today-I did not answer--will block the number.  They are still at it!!  ID was " Name Not Found".

7-10-14