Kernel-Based Virtual Machines (KVMs) are a powerful solution for optimizing cloud computing efficiency and security. Integrated into the Linux kernel, KVMs enable multiple virtual machines (VMs) to run on a single server with near-native performance, dynamic resource scaling, and minimal latency. They offer advanced resource optimization through memory ballooning and CPU overcommitment, ensuring cloud resources are used efficiently. Features like live migration allow seamless workload transfers without downtime. On the security front, KVMs provide strong VM isolation, Secure Boot, Trusted Platform Module (TPM) integration, and support for Security-Enhanced Linux (SELinux) and AppArmor for access control. With sVirt enforcing mandatory access controls and full-disk encryption for data protection, KVMs ensure robust cloud security. Additionally, tools like cgroups help manage resource limits, while VLANs and Open vSwitch (OVS) enhance network security. Used by public and private cloud providers alike, KVMs are ideal for high-performance computing, hybrid clouds, and mission-critical workloads. With their open-source nature, performance efficiency, and advanced security features, KVMs are essential for building scalable, cost-effective, and secure cloud environments.