Securing the Network Perimeter with Open Source & Common Sense

A few years ago, I was consulting at a large high-tech multinational on a network management project, when I learned about how they were protecting their network using almost entirely open-source tools and common-sense methods. I had seen (and applied) this same process in a smaller scale previously at significantly smaller customer sites where we didn't have the pockets to buy all the latest and greatest tool sets from the leading network security and management vendors, but never seen the solution truly scale.

Needless to say, I was impressed. It stuck in my mind, and as recent events have brought me back into researching network security trends, methods, and tools; the first thoughts I have been exploring are best practices for maximising security while minimising cost & resource impact.