For an active cable (lighning, etc.) look for new and look at the seller's feedback. Look at the other stuff they are selling. Is it junk, is it all off-brand? How long have they been selling?
It's not fool-proof and I still find myself buying only cable brands I trust (I don't mind overpaying for peace of mind when it comes to that). But the likelyhood of fakes (imitations of legitimate brands) is much lower, in my opinion.
eBay's opaque feedback system and captive seller relationships aren't the answer. The core problem is that they don't make it easy to associate individual listings with specific feedback for those items. In combination with the increasing popularity of "private" items, this encourages exit scams, among other things. A seller might garner 100% positive feedback for selling 500 Beanie Babies or whatever at $0.25 each, marking all the listings "private," then switch to ripping people off for $25K on nonexistent cars or machine tools or whatever.
eBay could easily fix this in the common case where bulk sales are involved simply by adding a "Show feedback for this item only" feature. But they care even less about providing effective search tools than Amazon does, which is really saying something.
Regardless of the question, the answer from the customer's point of view should involve more transparency rather than less. None of the major online retailers seem to agree, least of all eBay.
It's not fool-proof and I still find myself buying only cable brands I trust (I don't mind overpaying for peace of mind when it comes to that). But the likelyhood of fakes (imitations of legitimate brands) is much lower, in my opinion.