"Кто-нибудь знает что за песня?"

Does that mean "Nobody knows this song"? As in, "I have asked several times, but I can't find anybody who knows what song this is – this is my last attempt to find out...."

"Кто-нибудь знает."
I saw a translation of this saying "Somebody knows". Isn't that actually an incorrect translation?

So, for example if you were to say:
"Кто-нибудь знает секрет."

Does that mean "Somebody knows the secret" or "Nobody knows the secret"?