This morning I was trying to log on to Amazon's website when I got a red screen and an alarm as well as a message saying that my computer had been infected with pornographic software, and that my computer would be permanently disconnected from the internet if I didn't call a phone number that was provided in three places on the screen. The phone number was listed as belonging to Microsoft. It also froze my computer. To make a very long story short, This was bogus; a friend who is a retired software engineer did some digging and found that it is Microsoft policy to never to put it's phone number on an error message. He also found that this is a known scam. It does not infect your computer, but you will have to unplug it and reboot to get rid of it.
...if I'm taken somewhere I didn't intend, I hit power button ASAP, then run my antivirus software immediately after reboot. Likewise when an unfamiliar page takes longer than I think it should to load, sounds paranoid, but...
