I think Frozen Moat would not work on Stealth but does it work against Intinmidate?

Frozen Moat has no Response on it so when do you play it?

without double checking frozen moat i'm pretty sure it blanks before stealth. There is an action window after attackers are declared but before stealth is determined to be able use actions (look at lost oasis, you can give stealth before its declared and its a challenge action and not a response)

Lars is completely right. After declaring attackers there is an action window where the defender can activate frozen moat.