Software systems, containing security vulnerabilities, continue to be created and released to consumers. We need to adopt improved software engineering practices to reduce the security vulnerabilities in modern systems. These practices should begin with stated security policies and end with systems which are quantitatively, not just qualitatively, more secure. Currently, contracts have been proposed for reliability and formal verification; yet, their use in security is limited. In this work, we propose a contract-based security assertion monitoring framework (CB SAMF) that is intended to reduce the number of security vulnerabilities that are exploitable, spanning multiple software layers, to be used in an enhanced systems development life cycle (SDLC).