With respect to UL, you can go to
UL.com and find information on how to spot fakes, as well as a web based database search engine in which you can enter a UL file number and it will give you the name of the actual manufacturer and their file info that will tell you what it is listed for/as and where the listing label must be and what it must have on it. Often when counterfeiters do this, that’s a level of detail they don’t bother with. Also if the actual manufacturer shown on the product is not the same as what UL says, or the file number doesn’t match the product or description, those are major red flags.
IEC is I think more difficult when it comes to detecting counterfeits, because it is all “self certified”, there is no third party testing agency like UL. CE is a little better in that there are third party testing agencies that provide testing and certification, but some of the bigger companies can self certify as well. But CE listing is not indicative of what the product is supposed to do or how it performs, it is just mostly about its EMI/RFI emissions. I’ve seen people misinterpret this here in the US as if “CE listing” is the same thing as UL, when in truth it is nothing of the sort. I can get a CE label on a water bottle with two wires in it so long as when I connect the wires, they don’t cause interference in adjacent electronics.