A product authentication system and method employs a unique mark that is simple and cost-effective to apply and read, but provides several layers of protection, including anti-counterfeit and anti-diversion, against counterfeiters. The unique mark includes a bar code that is printed in invisible ink comprising a UV or near-IR ink and an IR mark. The first layer of protection is invisibility. The second layer of protection is the bar code itself. The third layer of protection is the presence of the IR mark in the unique mark. The fourth layer of protection is the IR emitting characteristics of the IR mark.