Now that Microsoft is getting out of the firewall business, many organizations are scrambling to start the process of deciding what they’ll use to replace ISA Server/TMG at the network edge and elsewhere. Some are considering pricey alternatives such as Cisco ASA appliances, but others are taking a look at alternatives that may be easier on the budget in these tough economic times. That includes building your own, based on open source software and powerful, inexpensive hardware.
If the idea catches your fancy, read more about it here:
https://www.infoworld.com/d/data-center/roll-your-own-firewalls-fun-and-profit-207547