One way to limit hostile sniffing on a LAN (Local Area Network is by installing:

A.
An Ethernet switch.

B.
An Ethernet hub.

C.
A CSU/DSU (Channel Service Unit/Data Service Unit).

D.
A firewall.

Explanation:
Sniffers can be mitigated using a Switch. The switch is intelligent and sends the data only to the destination
address. Sniffers usually work in a LAN using a hub.