[ben509]

One test is to search for something that's obviously a scam: '2TB flash drive'

You know these are scams because SSD chips with a high enough density to get 2TB in a keychain form factor are going to be cost thousands. When they're advertising $40 or $50, it's likely a 64GB drive with a controller that fakes the available storage.

Run some of those listings through FakeSpot and ReviewMeta to see how they do at identifying scams.