How to derermine if network has a sniffer?

Question

Is there a way to determine if network has a sniffer somewhere? I think one of my co-workers, with no right to monitor the network, has a sniffer installed somewhere. Is there a tool to determine and locate one?

Answer 1

Network sniffing is a passive operation, and as such is undetectable. Sniffers do not send any packets, so you don't even know that they are present.

Answer 2

If someone penetrates your internal network and puts in a sniffer, short of using IPSec, you're hozed. The only way to detect a sniffer is to go from node to node, one at a time, and manually search for an installed sniffer program....