Software Engineering Institute

With all the information available via NetFlows, finding the "Needle in the Haystack" (the bad actor in NetFlows), can be somewhat difficult at best. Methods to discover illegitimate traffic can be as simple as looking at TCP flags, to more complex procedures such as defining thresholds for number of flows with ratios to unique destinations. There are other methods available, but I will be focusing on these thresholds and ratios and why this approach turns the needle into a goal post. The CPU cycles needed for this analysis are reduced by implementation of AVL trees (Balanced Binary Trees), and knowing the bottleneck to process the data is based on reading the data from disc. The algorithm used takes less then a second to process 3 million flows collected over a 5 minute time span. Both inbound and outbound, as well as local, traffic needs to be considered. Inbound analysis will help protect against external threats, outbound traffic protects yourself from external embarrassment, and local analysis identifies local problems that can lead to bigger problems.