Abstract Physical Layer Security (PLS) is an emerging paradigm employed to enhance wireless network security without relying on higher-layer encryption techniques. PLS enables legitimate users to exchange confidential messages over a wireless medium in the presence of adversaries, by utilizing the main properties and characteristics of the wireless channel. Traditionally, security in wireless networks has been addressed separately from the physical layer due to its uncontrollable random nature. However, with the massive advances in computational capabilities, classical security techniques are becoming less secure and the need for new schemes is becoming more crucial. As a result, more and more research is directed towards studying, understanding and exploiting the highly random nature of wireless networks. This paper provides a comprehensive survey on various OFDM-based PLS techniques that target popular security services namely, key generation and distribution, data confidentiality, authentication, integrity and availability. With this survey, readers can have a better understanding of the PLS techniques present in the literature, their current limitations, challenges and countermeasures, in addition to future research directions in this area.