Critical materials are inputs that are strategically important and may be vulnerable to supply disruption. In security and defense contexts, the term usually refers to metals, minerals, chemicals, or other raw inputs that a program cannot easily replace without cost, delay, or operational risk.
They matter in cyber security because modern attacks often begin before software is even deployed. If an adversary can introduce counterfeit, substituted, or poorly vetted materials into a hardware supply chain, the result may be insecure devices, hidden faults, or weakened reliability. Defenders use sourcing controls, vendor verification, traceability, and documentation to prove where materials came from and who handled them. In practice, treating critical materials as a security issue helps organizations reduce supply-chain tampering and strengthen trust in the systems they build.