I have a gently used dell optiplex 3020 with an i3-4150 2 core, 4 thread CPU. It is equipped with 8GB of RAM, a dual port intel gigabit NIC and a 500GB HDD. All this makes running a fresh installation of pfSense a breeze. This firewall software is highly customizable, including possibilities for IPS/IDS, ad blocking, etc. The BIOS can be configured to disable the USB ports as well as sense chassis intrusion. Your home or small business network can be tailored to your specific needs. More information on the firewall software can be found here.
https://www.pfsense.org/getting-started/
