Specs:
Celeron E1200 Dual Core @ 1.6GHz
2GB DDR2 RAM
80GB Sata HDD
Onboard Gigabit and Intel Gigabit Card

Looking for a Linux based/Open-Source Firewall OS that offers real time virus scanning, ad-blocking, IPS, IDS, and is Free.

I put this in this section, because I didn't see another more appropriate section. Thanks.