Direct Equivalents:
* Wolf in sheep's clothing: This is the most literal and well-known expression.
* A viper in the bosom: This emphasizes the danger of someone who seems trustworthy but is secretly harmful.
Figurative Equivalents:
* A Trojan horse: This refers to something seemingly harmless that hides a threat within.
* A snake in the grass: This signifies a hidden enemy or danger.
* A fair face, a foul heart: This describes someone with a pleasant appearance but evil intentions.
* All that glitters is not gold: This means that appearances can be deceiving.
* Don't judge a book by its cover: This warns against making assumptions based solely on outward appearances.
Other expressions:
* Beware of Greeks bearing gifts: This is a warning to be suspicious of gifts from those who might have ulterior motives.
* He who smiles too much has something to hide: This suggests that excessive friendliness can be a sign of deception.
* A wolf in wolf's clothing: This is a humorous way to say someone is obvious in their deceit.
The best idiom to use will depend on the specific context and the nuance you want to convey.