An investigation of hotlinking and its countermeasures

Hotlinking is a web behavior that links web resources on a hosting site into a webpage belonging to another site. However, unauthorized hotlinking is unethical, because it not only violates the interests of hosting sites by consuming bandwidth and detracting site visiting traffic but also violates the copyrights of protected materials. To fully understand the nature of hotlinking, we conduct a large-scale measurement study and observe that hotlinking widely exists over the Internet and is severe in certain categories of websites. Moreover, we perform a detailed postmortem analysis on a real hotlink-victim site. After analyzing a group of commonly used hotlinking attacks and the weakness of current defense methods, we present an anti-hotlinking framework for protecting materials on hosting servers based on existing network security techniques. The framework can be easily deployed at the server-side with moderate modifications, and is highly customizable with different granularities of protection. We implement a prototype of the framework and evaluate its effectiveness against hotlinking attacks.