The text aims at measuring digital literacy among teachers of the third stage of education in Poland (lower secondary schools). The study was commissioned by the Ministry of National Education and was conducted in 2018 in Poland, and involved a group of 484 teachers. The goal of the research was to present the teachers' knowledge and skills related to digital threats in the areas of the assessment of the reliability of information, sexting, cyberbullying, intellectual property rights, the protection of online images, and protection against malware. Digital literacy (DL) was measured using a knowledge and competence test and a diagnostic survey. The ability to enter the LLL process thanks to the ongoing advancement of ICT increases the online safety of all of the school-related stakeholders. A detailed analysis of the results also revealed that the teachers obtained good results in the test in terms of their knowledge about sexting and image protection but scored poorly regarding copyright and the assessment of the reliability of online information; male teachers know more about the technical aspects of digital safety than female teachers; trainees need particular support in the form of informal and non-formal education.