Computer security is a technical discipline focused on protecting computer systems, networks, and data from unauthorized access, misuse, modification, or denial of service. The core objectives are maintaining confidentiality, ensuring data integrity, and guaranteeing system availability. Defense mechanisms include employing strong access control policies, implementing firewalls and intrusion detection systems to monitor traffic, and utilizing cryptographic techniques to encrypt sensitive information both in transit and at rest. Effective security practices require continuous vigilance against evolving threats, such as malware, exploits, and sophisticated network attacks, necessitating the development of multilayered protective frameworks to maintain operational resilience.