Amazon Mechanical Turk is an extremely useful platform which can be used to obtain large amounts of data with minimal amount of effort. One of the possibilities of the Human Intelligence Task (HIT) is the transciption of audio files. The main problem that stems from the platform is a user attempting the same task multiple times and giving identical answers to what he/she did the first time. This results in the biasing of data which interferes and hampers the research that this data is required for. Amazon Mechanical Turk attempts to solve this problem by using the QualificationID parameter for each user. This parameter can be modified to prevent the same user from attempting the same task more than once.
However, Turkers can circumvent this by making multiple accounts. In order to counter that, cookies are used. These cookies are embedded into the browser the first time the user accesses the task. The subsequent efforts in accessing that task (if using a different account) results in the cookie being recognized. A request is then sent to the Mechanical Turk server which changes the QualificationID of the Turker to that of a user who has already accessed the task once. Turker is then invalid for the task and is rejected from accessing it.