Will avast automatically scan newly downloaded files to prevent infections? My son often downloads things and it is a concern. Thanks!
What avast version are you using 4.8 or 5.0 ?
A lot depends on how these files are downloaded and by what.
P2P, Download Manager or just through the browser, etc. ?
The P2P Shield should monitor p2p traffic, e.g. downloads.
Using a download manager, most have an ability to have your AV scan the completed download, failing that depending on the file type downloaded the avast on-access scanner should scan them.
The web shield should monitor http port 80 traffic (normal browsing and downloads using the browsers download function).
So with more information we can be more detailed in an answer.