Abstract-Internet is considered a Critical Infrastructure (CI) that is vital for both the economy and the society. Disruptions caused by natural disasters, malicious human actions and even hardware failure pose serious risks. Emulation testbeds are increasingly used to study the Internet in order to improve protection and response mechanisms. These are frequently considered more adequate than software simulators to realistically recreate the complex behavior of networks. In this paper we study how testbeds based on the Emulab software can be used to conduct scientifically rigorous experiments, specifically in terms of: a) experiment fidelity, b) repeatability, c) measurement accuracy, and d) interference.Our study, which is based on extensive experimentation on different testbeds, indicates that the current trend of using emulation testbeds is justified as both realistic and efficient. We show that Emulab-based experiments are representative of real systems in terms of emerging behavior (qualitative) and that repeatable experiments are possible. The main contribution of this tutorial article is that based on experimental results we identified caveats and provided insights to significant configuration parameters and limitations that are further elaborated into a set of guidelines that any Emulab user should be aware of. Then, he/she can decide about the importance of each guideline in the context of a specific study and experiment.

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Shodan has been acknowledged as one of the most popular search engines available today, designed to crawl the Internet and to index discovered services. This paper expands the features exposed by Shodan with advanced vulnerability assessment capabilities embedded into a novel tool called Shodan‐based vulnerability assessment tool (ShoVAT). ShoVAT takes the output of traditional Shodan queries and performs an in‐depth analysis of service‐specific data, that is, service banners. It embodies specially crafted algorithms which rely on novel in‐memory data structures to automatically reconstruct Common Platform Enumeration names and to proficiently extract vulnerabilities from National Vulnerability Database. Compared with the state of the art, ShoVAT brings several novel and significant contributions because it encompasses automated vulnerability identification techniques, it can return highly accurate results with customized and even purposefully modified service banners, and it supports historical service vulnerability analysis without the need to deploy additional monitoring infrastructures. The experiments performed on 1501 services in 12 different institutions across different sectors revealed high accuracy of results and a total of 3922 known vulnerabilities. Copyright © 2015 John Wiley & Sons, Ltd.