walls have ears

Walls have ears. (something that you say in order to warn someone to be careful what they say because someone may be listening or you think your conversation is being overheard) — и стены имеют уши; нас могут услышать

Example 1: Jill: Did I tell you what I found out about Fred? He—Jane: Shhh! Walls have ears.

Example 2: Don't say anything about our business dealings in here. Walls have ears.. (McGR)

Example 3: Why don't we go and talk about this somewhere quieter? Walls have ears, you know.

Example 4: Walls have ears and you should think carefully about what you say when you are talking about your co-workers.

see also
[loose lips sink ships]