The rules don't seem to say what are defense traits for the
statue
and they don't seem to say what the traitor attacks with?
The Traitor's tome intentionally doesn't cover the [spoiler]
That's up for the Heroes to let the traitor know. The Secret's of survival book has all the rules for
attacking the statue.
Here's the relevant bits from the Secrets of Survival book:
Once the Statue animates, it remains in whatever state it transformed into for the rest of the game. When the Statue has been animated, tell the traitor what form it has taken. If the traitor attacks the Statue and defeats it, it isn’t stunned. Instead, the Statue can’t lower an ability during its next turn. The Statue can still be moved to follow the traitor.
So this is how it works:
The traitor can attack the Statue normally, and the heroes should let the traitor know so when it animates. The traitor attacks with the default might, and the statue defends with might, as normal in any combat - unless an item says differently (like The Ring allows you to attack with Sanity). The Statue's attributes are 8 for everything (Speed, Might, Sanity and Knowledge) and it defends with the appropriate attribute for the attack.