If you are refering to installing it on one PC and scanning your LAN with that one program it is done in many cases but with a big expense. They have gateway hardware that can be installed as your first defense that will scan all traffic coming and going through your LAN.You can also set one PC up and use ICS,that will be your gateway and can probably get software to scan traffic.It can be done but it is involved and expensive.You have done the best thing with filtering ,spyware, antivirus etc.software. Install on each PC in your LAN.there are a lot of great free software to take care of all the hasles of surfing the Net.