The publishing model based on author fees has increased the number of predatory journals and book publishers. Characteristic features of the predator include low-quality webpages, fast processing time of manuscripts, a vague topic, aggressive email marketing and lack of contact information. Author fees alone do not make the journal suspicious, but any doubt regarding the size of the fees, the composition of the editorial board, database indexing and impact factor information or the peer review implementation is a good reason to leave the journal at Level 0.