The Internet is a complex system of autonomous but cooperating networks that constitute a critical Infrastructure with a vast socio-economic significance. Any disruption of the Internet and its services has detrimental effects to its users, be it in the private sector or the industry. This is why Internet research aims for observing, mitigating, and ultimately preventing attacks.
In this thesis, we provide methodologies to evaluate and extend the coverage of attack observations, we assess the efficacy of current and emerging attack mitigation solutions, and we identify new opportunities for attack prevention. We do so by utilizing two major vantage point positions, the Internet core and the Internet edge. Our contributions have an operational impact on today's Internet but also its future deployment.