  Employing paraphrasing tools to conceal plagiarized text is a severe threat
to academic integrity. To enable the detection of machine-paraphrased text, we
evaluate the effectiveness of five pre-trained word embedding models combined
with machine learning classifiers and state-of-the-art neural language models.
We analyze preprints of research papers, graduation theses, and Wikipedia
articles, which we paraphrased using different configurations of the tools
SpinBot and SpinnerChief. The best performing technique, Longformer, achieved
an average F1 score of 80.99% (F1=99.68% for SpinBot and F1=71.64% for
SpinnerChief cases), while human evaluators achieved F1=78.4% for SpinBot and
F1=65.6% for SpinnerChief cases. We show that the automated classification
alleviates shortcomings of widely-used text-matching systems, such as Turnitin
and PlagScan. To facilitate future research, all data, code, and two web
applications showcasing our contributions are openly available.
