The document discusses security breaches that occur through third party systems and vendors. It describes how attackers were able to access Target's corporate network by compromising a refrigeration contractor called Fazio Mechanical through a phishing email. This allowed malware called Citadel to be installed on Fazio computers. The document also discusses the importance of implementing a secure software development lifecycle (SDLC) and using tools like Dimensions CM to integrate code reviews, continuous inspection, and maintain a centralized secure vault for source code repositories.