If it loads it is real
If the address loads the login page, it is the real site
Three questions called one word
- Does it load
- The weakest sense and the one most people mean. A clone loads. It loads faster than the real platform, because it has no traffic and no defences to run.
- Is it current
- Whether the address is still in use rather than retired. Better, checkable against a list, and a list is only as good as its source.
- Is it genuine
- Whether the party answering holds the key it claims. The only question with a definitive answer, and the answer comes from a signature rather than anything visible on the page.
Why the first two mislead
They correlate with the third in ordinary conditions, which is exactly what makes them dangerous. Most of the time a current address that loads is genuine, so the habit of checking only those works most of the time and quietly builds confidence.
It fails precisely in the situation it was meant to protect against, which is when somebody has gone to the trouble of building a convincing clone. A heuristic that works except when attacked is not a defence.
What settles it
A signature verified against a fingerprint you established independently. That establishes two things and only two: that whoever signed held a specific private key, and that the signed text is unchanged. Narrow, absolute, and the only thing available that answers the question at all.
The dependency is the fingerprint. A signature checked against a key taken from the page you are checking proves nothing, because the page, the key and the signature all came from the same party and internal consistency is free for a forger. The verifying page covers establishing one properly.
A link somebody sent you
Treat the source as carrying no information at all. A link from a forum you have read for years, a person you trust, or a site that has been right before is exactly as unverified as one from a stranger. Not because those sources are dishonest, but because none of them can prove anything about an address, and the thing that can takes under a minute.