This course aims to provide an overview of cybersecurity. Most topics of cybersecurity are covered (attacks, malware, security policy, security mechanisms, user authentication, symmetric and asymmetric Cryptography, network security, personal data protection). For each type of attack or malware, we propose some solutions to prevent them. Regarding security policy, we present the Discretionary Access Control (DAC) policy and several types of Mandatory Access Control (MAC) policy. We also review the main existing tools to control information flows in a network, like a firewall or proxy server. We present several ways to authenticate a user like a password or two-factor authentication. We give a comprehensive overview of the main cryptographic mechanisms for encryption and integrity protection. We review several uses of asymmetric encryption like digital signatures or symmetric key exchange. We also address the issue of personal data protection and give an overview of the European General Data Protection Regulation (GDPR).