Computer Help and Support

It installs Windows services and one of those would be to connect to the net, overriding other settings to check for updates etc.

The only way to turn it off is to uninstall Avast, for which you may need a special program and a couple of restarts. You may not be keen to do this, but windows security is much better than it used to be and for a couple of years now, I've dispensed with outside anti-virus programs and use only the native windows services.

We are a much more sophisticated bunch of computer users than we were ten or twenty years ago. We know not to open dodgy attachments; the main danger is malicious web pages and code. There is an add-on for Firefox called NoScript that you can tweak to prevent the execution of malicious code when you browse. It's definitely worth getting used to. There are a few similar clone add-ons.

Feel free to PM if you like.