A former student of the University of Iowa has been arrested by the Federal Bureau of Investigation for hacking school  and changing his results.

According to the New York Times, Trevor Graves, 22, is accused in an FBI affidavit of working with an unnamed accomplice to secretly plug keyloggers into university computers in classrooms and in labs.

The FBI says keyloggers allowed Graves to record whatever his professors typed, including credentials to log into university grading and email systems.

Court documents allege that Graves intercepted exams and test questions in advance and repeatedly changed grades on tests, quizzes and homework assignments. This went on for 21 months – between March 2015 and December 2016.

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The FBI affidavit claims that Graves changed his grades more than 90 times during those 21 months. He also allegedly changed grades on numerous occasions for at least five of his classmates.

The scheme was discovered when a professor noticed that a number of Graves’ grades had been changed without her authorization. She reported it to campus IT security officials.

The FBI said it spoke with one student who told them that Graves shared copies of about a dozen exams before students sat down to take them. According to the FBI, the student said that he/she accepted the stolen exam, given that everybody else was doing it and they didn’t want their grade to suffer in comparison

The university told the FBI that the cheating scheme cost the school $68,000 to investigate the breach and to beef up its IT security.