Reader James McClellan, who is also a friend, wrote several weeks ago to say:
When I booted up Thursday evening I got a message from my Microsoft antispyware that my fire wall and virus protection were turned off.
I went to Norton and sure enough, both were turned off and wouldn’t turn on.
I ran live update, rebooted the computer and everything is fine. I also reran all my scan (i.e. spyware, virus, etc.)
I responded to James immediately. I also think this is worth mentioning to you, too.
That is really not a good sign. There are some viruses and other malware that first aim at the firewall and antivirus, and turn them off if they can. At that point, your computer is fair game…
All three offer a 30 day full-function trial, and give both always-running and scheduled/on-request scanning functions.
Check my Anti-virus programs page for links for free online antivirus scans. Use one or both (at different times). Use the online scanner from someone other than your supplier of your AV program. Note that most online antivirus scanners are exactly that — scanners; they don’t do repairs.
I have run into this problem once before, and wrote much more about it in my Was it a premonition or just coincidence? article in one of my email newsletters.