A plagiarism detection procedure in three steps: Selection, matches and squares

Abstract

We present a detailed description of an algorithm tailored to detect external plagiarism in PAN-09 competition. The algorithm is divided into three steps: a first reduction of the size of the problem by a selection of ten suspicious plagiarists using a n-gram distance on properly recoded texts. A search for matches after T9-like recoding. A "joining algorithm" that merges selected matches and is able to detect obfuscated plagiarism. The results are briefly discussed.