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Sooner or later, a user may see that his answers are getting a lot of up-votes, then he gets a large negative reputation change labelled "voting corrected". This is because a user has voted on the answers in a short period of time, and then the system detects it and deletes the votes. Obviously, this is to protect the site from scripts, sock puppetry, or from people sorting answers by author, not content.
I have heard that you should avoid "five votes in a row", but how exactly is unusual voting behaviour detected? Is the exact algorithm classified?