Flow monitoring has become a prevalent method for monitoring traffic in high-speed networks. By focusing on the analysis of flows, rather than individual packets, it is often said to be more scalable than traditional packet-based traffic analysis. Flow monitoring embraces the complete chain of packet observation, flow export using protocols such as NetFlow and IPFIX, data collection, and data analysis. In contrast to what is often assumed, all stages of flow monitoring are closely intertwined. Each of these stages therefore has to be thoroughly understood, before being able to perform sound flow measurements. Otherwise, flow data artifacts and data loss can be the consequence, potentially without being observed. This paper is the first of its kind to provide an integrated tutorial on all stages of a flow monitoring setup. As shown throughout this paper, flow monitoring has evolved from the early nineties into a powerful tool, and additional functionality will certainly be added in the future. We show, for example, how the previously opposing approaches of Deep Packet Inspection and flow monitoring have been united into novel monitoring approaches.

The security of information technology and computer networks is effected by a wide variety of actors and processes which together make up a security ecosystem; here we examine this ecosystem, consolidating many aspects of security that have hitherto been discussed only separately. First, we analyze the roles of the major actors within this ecosystem and the processes they participate in, and the the paths vulnerability data take through the ecosystem and the impact of each of these on security risk. Then, based on a quantitative examination of 27,000 vulnerabilities disclosed over the past decade and taken from publicly available data sources, we quantify the systematic gap between exploit and patch availability. We provide the first examination of the impact and the risks associated with this gap on the ecosystem as a whole. Our analysis provides a metric for the success of the "responsible disclosure" process. We measure the prevalence of the commercial markets for vulnerability information and highlight the role of security information providers (SIP), which function as the "free press" of the ecosystem. IntroductionWith the ongoing deployment of information technology in today's economy and society, comprehending the evolution of information security at large has become much more than the mere understanding of the underlying technologies. There is

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Status of This Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.