Cloud computing provides on-demand access to computing resources and IT services over the Internet. While cloud computing provides scalability and cost savings, security is a major concern due to issues like data breaches, multi-tenant infrastructure sharing user data, and lack of governance over cloud provider control of resources. Virtualization is key to cloud computing but introduces vulnerabilities if not implemented securely. Data security risks include exposure of data at rest in cloud storage and data in transit between cloud systems. Strong authentication, encryption of data in transit and at rest, and use of private clouds can help address these security issues but securing cloud systems remains a major challenge.