A counterfeit part is an unauthorized copy, imitation or substitute, or a used part passed off as new. Electronic components get the most attention, but fasteners, bearings, raw material and other commodity parts are counterfeited too. In aerospace and defense the consequences are serious enough that AS9100D makes counterfeit parts prevention an explicit requirement (clause 8.1.4).
AS9100D asks you to plan and implement processes that prevent counterfeit or suspect counterfeit parts from being used and from reaching your customer. In practice that means training people to recognise the risk, buying from trustworthy sources, verifying what you receive, controlling suspect parts, and reporting them. Your customers may add their own requirements through purchase order flow-downs, so check those too.
Quarantine suspect parts, record them as nonconforming product and do not return them to the supplier where they could re-enter the supply chain. Investigate how they got in, raise a corrective action, and report as your customer and any applicable reporting systems require.
Purchasing, receiving inspection and stores staff are your first line of defense. Keep training records, and refresh the training as risks change.
FactoryQA keeps the pieces in one system: the approved supplier list with scope and certificates in Supplier Quality, nonconforming and suspect parts and their corrective actions in Issues, and training records in Learning Management. Compliance scores your readiness against AS9100D, clause by clause.