PC or Linux Firewall
You won’t get the cleverest of the filtering features for free, but you will get a machine that has enough ability to keep the secured side of the network suitably safe. Is a roll-your-own approach as good or better than paying for specialised devices?
Cost is the advantage most commonly quoted. If suitable hardware is already available, the effective cost of a hand-built Linux firewall is effectively zero. Having total control of the configuration at every level allows for a device ideally tailored for the network environment. But PC-based firewalls have specific problems too. They are always inherently more unreliable than hardware specifically designed for the task – old PSUs and hard disks don’t last forever!
But the biggest problem is the expense of managing PC-based firewalls. Updating and maintenance requires a higher level of skill: the people responsible need to be skilled in Linux setup and configuration, as well as firewall configuration. Planning and preparation for catastrophic events such as firewall failure must be done in-house and in advance – which means a stock of spare parts up to and including motherboards (especially if the hardware is elderly) and procedures for rolling out a replacement at speed if necessary.
It’s certainly worth considering Linux- based firewalls but the question to ask is “What could go wrong, and how easy is it to mitigate those situations?”
The answers may show that even though they are near-free, the hidden costs could outweigh the benefits.