alanrf
3
If I understand this correctly you are running a machine with just an operating system and antivirus on it. Since you mention ICS I am guessing that machine is basically acting as your hub allowing the sharing of your Internet connection between the other systems.
While I hate to mention the sack of hammers …
Any regular antivirus program scans only the activity that originates on the machine on which it is installed. avast will only scan the browser traffic generated on that machine.
The ICS connections to the other machines are, to the very best of my knowledge, flying under the radar of any antivirus program installed on the main ICS system. So all of the other systems are operating without any antivirus protection.
You would need to install avast on each of the systems to ensure scanning of the activity on each system.