The production and distribution of counterfeit parts is rising and finding their way into consumer and military devices. As counterfeiters get more sophisticated, so must the tests used for detecting counterfeit parts. A functional test strategy can provide an additional detection methodology that will exercise the device under a variety of operating conditions exposing functional deficiencies. This paper will discuss how establishing a functional baseline will define the bar for functional performance and can be very effective in detecting and stopping counterfeit parts from being shipping in assembled electronic devices.  It describes how Verification and Test OS (VTOS™) provides an extensive functional test library that can be easily extended or modified to create an operational baseline to be used to detect counterfeit parts. VTOS can be used in engineering, as well as manufacturing, providing test consistency while in search for counterfeit parts.  If functional testing is missing from your test strategy, now may be the time to reconsider its benefits.