A broad range of research areas including Internet measurement, privacy, and network security rely on lists of target domains to be analysed; researchers make use of target lists for reasons of necessity or efficiency.

The popular Alexa list of one million domains is a widely used example. Despite their prevalence in research papers, the soundness of top lists has seldom been questioned by the community: little is known about the lists’creation, representativity, potential biases, stability, or overlap between lists.

In this study we survey the extent, nature, and evolution of top lists used by research communities. We assess the structure and stability of these lists, and show that rank manipulation is possible for some lists. We also reproduce the results of several scientific studies to assess the impact of using a top list at all, which list specifically, and the date of list creation. We find that (i) top lists generally overestimate results compared to the general population by a significant margin, often even an order of magnitude, and (ii) some top lists have surprising change characteristics, causing high day-to-day fluctuation and leading to result instability.

We conclude our study with specific recommendations on the use of top lists, and how to interpret results based on top lists with caution.

About Julien Gamba

Julien Gamba is a PhD student in the Internet Analytics Group at the IMDEA Networks Institute. He graduated from the university of Strasbourg (France) in 2017 with a master degree in computer networks and embedded systems with honors. Before joining IMDEA Networks, he was a research assistant at the iCube laboratory in Strasbourg, working on conception rules for iBGP networks to ensure BGP correctness. He also was a research assistant at Internet Initiative Japan in Tokyo, working on the fragmentation of the BGP routing table.

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