Marking a petroleum product includes adding a covert dye selected from the group consisting of azadipyrromethene dyes, dipyrromethene dyes, and any combination thereof to the petroleum product and distributing the dye in the petroleum product. A petroleum product selected for analysis may be spectroscopically analyzed for the presence of an azadipyrromethene dye, a dipyrromethene dye, or a combination thereof. A concentration of at least one azadipyrromethene or dipyrromethene dye present in the portion of the petroleum product may be determined to identify the petroleum product as counterfeit, adulterated, or authentic based on the determined concentration of the azadipyrromethene or dipyrromethene dye.