I took a brief peek at the paper cited by the article (<a href="http:&#x2F;&#x2F;theory.stanford.edu&#x2F;~aiken&#x2F;publications&#x2F;papers&#x2F;sigmod03.pdf" rel="nofollow">http:&#x2F;&#x2F;theory.stanford.edu&#x2F;~aiken&#x2F;publications&#x2F;papers&#x2F;sigmod...</a>) to see how the system worked. It uses hashes of n-grams of the submitted programs to compare similarity.<p>My own experience with plagiarism came when teaching a university course for CS majors. For most, the class was their second course in programming. While grading an early programming assignment I noticed a program that reminded me of one of the early ones I had already graded. Comparing the two programs revealed that they were identical, except that the variable names had been changed to protect the guilty.<p>I wonder if this system would have detected this case of collaboration.