In the last twenty years, the Internet has grown from a simple, small network to a complex, large-scale system. While the Internet was originally used to offer static content that was organized around simple websites, today, it provides both content and services (e.g. chat, e-mail, web) as well as the outsourcing of computation and applications (e.g. cloud computing). In 2011, the number of Internet users has surpassed two billion (i.e., a third of the global population) and the number of Internet hosts are approximately 800 million. Websites are reachable via a wide range of computing devices such as personal computers, tablet PCs, mobile phones.
Also, users often have anywhere, any time access to the Internet.Attackers are not indifferent to the evolution of the Internet. Often driven by a flourishing underground economy, attackers are constantly looking for vulnerabilities, misconfigurations and novel techniques to access protected and authorized systems, to steal private information, or to deliver malicious content. Traditional vulnerabilities such as buffer overflows or SQL injections are still exploited. However, new alternative attack vectors that leverage unconventional channels on a large scale (e.g. cloud computing) are also being discovered. To date, not much research has been conducted to measure the importance and extent of these emerging Internet threats. Conventional detection techniques cannot easily scale to large scale installations, and novel methodologies are required to analyze and discover bugs and vulnerabilities in these complex systems. In this thesis, we advance the state-of-art in large scale testing and measurement of Internet threats. We research into three novel classes of security problems that affect Internet systems that experienced a fast surge in popularity (i.e., ClickJacking, HTTP Parameter Pollution, and commercial cloud computing services that allow the outsourcing of server infrastructures). We introduce the first, large scale attempt to estimate the prevalence and relevance of these problems on the Internet.