Supply Chain Attacks exploit trusted relationships between organizations and their software vendors, service providers, or hardware suppliers to gain unauthorized access. Attackers compromise a supplier's products or services, then leverage legitimate distribution channels to infiltrate multiple downstream customers simultaneously. The SolarWinds breach of 2020 infected approximately 18,000 organizations through a compromised software update, demonstrating the cascading impact of supply chain vulnerabilities. Prevention requires vendor security assessments, software bill of materials analysis, code signing verification, and continuous monitoring of third-party components. These attacks are particularly dangerous because they bypass perimeter defenses by entering through trusted channels.