Prov. Someone may be listening. (A warning that you think your conversation is being overheard.) Jill: Did I tell you what I found out about Fred? He—Jane: Shhh! Walls have ears. Don't say anything about our business dealings in here. Walls have ears.
something that you say in order to warn someone to be careful what they say because someone may be listening Why don't we go and talk about this somewhere quieter? Walls have ears, you know.