document: Serf and turf : crowdturfing for fun and profit Popular Internet services in recent years have shown that remarkable things can be achieved by harnessing the power of the masses using crowd-sourcing systems . However , crowd-sourcing systems can also pose a real challenge to existing security mechanisms deployed to protect Internet services . Many of these security techniques rely on the assumption that malicious activity is generated automatically by automated programs . Thus they would perform poorly or be easily bypassed when attacks are generated by real users working in a crowd-sourcing system . Through measurements , we have found surprising evidence showing that not only do malicious crowd-sourcing systems exist , but they are rapidly growing in both user base and total revenue . We describe in this paper a significant effort to study and understand these `` crowdturfing '' systems in today 's Internet . We use detailed crawls to extract data about the size and operational structure of these crowdturfing systems . We analyze details of campaigns offered and performed in these sites , and evaluate their end-to-end effectiveness by running active , benign campaigns of our own . Finally , we study and compare the source of workers on crowdturfing sites in different countries . Our results suggest that campaigns on these systems are highly effective at reaching users , and their continuing growth poses a concrete threat to online communities both in the US and elsewhere .
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