"WARNING! Your Flash Player may be out of Date. Please upgrade to continue. "

I try to go on facebook, youtube, google or Yahoo, and it's opening a page with an announce: "WARNING! Your Flash Player may be out of Date. Please upgrade to continue. " I can click only "ok", then it opens a page of "FLASH PLAYER PRO", and it would me to download a trojan virus (avira recognized it) called "setup.exe.". I know that is a viral page that maybe is stealing the name of "Flash Player Pro ", but how is possible to stop it? The plug-in on the pc has the same name of "shockawave flash" ; I tried to: cancel cookies, changing antivirus, istalling flash player 13 from the official site, cancelling every adobe flash player of the pc. Blocking the site is unusefull because they have'nt an IP address and they steal the IP address of the site you choose. I've a Windows 7 professional 32 bit and I try with: Firefox, Chroome, Opera, Explorer. Nothing.  Does anybody knows how can I stop it?

I wrote this post in "Installing flash player" because maybe is an installation problem... I don't know.

Thank you!!