The Awazon captcha does two jobs. It slows automation, and it gives you a way to catch a phishing clone in a single glance.
The puzzle
Six characters of text, case sensitive. Read the case carefully, because a lower-case letter typed as a capital fails the check. It is deliberately simple for a human and awkward for a script.
The embedded address
The genuine login renders the market's own onion address into or beside the captcha image, generated server-side in the same file the browser downloads. Your job is to compare that printed address against the one in your browser bar before you type a password.
Why a clone struggles to fake it
A phishing site can copy the Awazon theme in minutes. What it cannot easily do is serve the correct Awazon address inside the captcha while your bar shows the clone's address. The two will not match, and the mismatch is the tell. Do this check every session, not just the first, because a bookmark can go stale between rotations.