The Self-service cloud computing model splits administrative privileges between a system-wide domain and per-client administrative domains. As user clients have administrative privileges there is a possibility for clients to be malicious. In order to detect these malicious clients we introduce a Virtual shield in the system-wide domain. The Virtual Shield (which is a detection model) is a new computing model designed to detect denial of service attack (with respect to RAM usage), side channel attack (with respect to bandwidth usage) and a combined attack for a large population of clients. Results show that our proposed approach detects these attacks with small false positive/negative error rate and low latency. The Virtual Shield has the capability to handle individual attacks and a combined denial of service and side channel attacks.