In order to evaluate the prevalence of security and privacy practices on a representative sample of the Web, researchers rely on website popularity rankings such as the Alexa list. While the validity and representativeness of these rankings are rarely questioned, our findings show the contrary: we show for four main rankings how their inherent properties (similarity, stability, representativeness, responsiveness and benignness) affect their composition and therefore potentially skew the conclusions made in studies. Moreover, we find that it is trivial for an adversary to manipulate the composition of these lists. We are the first to empirically validate that the ranks of domains in each of the lists are easily altered, in the case of Alexa through as little as a single HTTP request. This allows adversaries to manipulate rankings on a large scale and insert malicious domains into whitelists or bend the outcome of research studies to their will. To overcome the limitations of such rankings, we propose improvements to reduce the fluctuations in list composition and guarantee better defenses against manipulation. To allow the research community to work with reliable and reproducible rankings, we provide Tranco, an improved ranking that we offer through an online service available at this https URL.
@cite_9: This study examines the similarities and differences among several publicly available website ranking lists to determine how reliable the lists are. Several metrics were used to measure the concordance and discordance of these lists. The effect of list size was investigated. Practical implications for e-business advertising costs and the review of search engine results are discussed.
In 2006, Lo and Sedhain @cite_9 studied the reliability of website rankings in terms of agreement, from the standpoint of advertisers and consumers looking for the most relevant sites. They discussed three ranking methods (traffic data, incoming links and opinion polls) and analyzed the top 100 websites for six providers, all of which are still online but, except for Alexa, have since stopped updating their rankings.