document: Spam double-funnel : connecting web spammers with advertisers Spammers use questionable search engine optimization ( SEO ) techniques to promote their spam links into top search results . In this paper , we focus on one prevalent type of spam - redirection spam - where one can identify spam pages by the third-party domains that these pages redirect traffic to . We propose a five-layer , double-funnel model for describing end-to-end redirection spam , present a methodology for analyzing the layers , and identify prominent domains on each layer using two sets of commercial keywords . one targeting spammers and the other targeting advertisers . The methodology and findings are useful for search engines to strengthen their ranking algorithms against spam , for legitimate website owners to locate and remove spam doorway pages , and for legitimate advertisers to identify unscrupulous syndicators who serve ads on spam pages .
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