All versions of Avast has the same detection rate. The sandbox is incorporated in all of them. But this wasn’t a program that was downloaded. It was most likely a link your father clicked on via an email. Using a 3rd party browser such as Firefox or Google Chrome is a start. Adding Adblock Plus and WOT to either of those is also wise. I already listed the antiviruses which I have seen miss this. You also have to understand that the people who makes this change the code daily. Avast still has one of the highest detection rates around. So honestly speaking Avast isn’t really to blame here as much as how your father came across this. Ask him what he was doing or what he clicked on.

The best protection is to keep a clean system image that is current and up to date. If this happens simply mount the stored image and your up and running like nothing every happened. Prevention is better then detection any day.