Short answer: Ordinary search engines do not index .onion. Ahmia filters .onion indexes. DuckDuckGo offers clearnet search over Tor. Search results can contain phishing — always verify.
Why special search engines?
Google and Bing do not crawl .onion addresses. Finding hidden services requires Tor-native indexes or curated directories such as TorBible sources.
Ahmia
Ahmia indexes .onion sites and actively filters abusive content. It is run by a Finnish security researcher and has received some Tor Project support. Official .onion address in the search engine directory.
DuckDuckGo over Tor
DuckDuckGo operates a .onion front end for private clearnet search — without tracking. It does not index .onion sites directly.
Phishing risk
Search results and directories list content without complete verification. Check every .onion address against at least two independent primary sources. More: Detecting phishing.
Curated alternative
Instead of unfiltered search: the link directory with primary sources only — Tor Project, SecureDrop, legitimate tools.