This module explains how supply chain attacks in crypto exploit trusted third-party components (libraries, APIs, dev tools) to stealthily insert malicious code. Real-world cases, such as compromised npm/PyPI packages and the @solana/web3.js backdoor, highlight the vast scale and severity of such attacks. Key prevention strategies include vetting dependencies, automated scanning, secure CI/CD, vendor management, and team training. As crypto ecosystems grow increasingly interconnected, safeguarding every layer—from code dependencies to build pipelines—is essential to protect funds, reputation, and regulatory compliance.