Detect whether Sniffer exists in your network.

Nmap can be a tool to verify whether there is any sniffer running in your network.

Here is an example of using Nmap to address the sniffer, and 192.168.30.29 is the PC hosting a sniffer.

root@is:~# nmap -sn --script=sniffer-detect 192.168.30.0/24

Starting Nmap 7.40 ( https://nmap.org ) at 2018-07-06 11:27 EDT
Nmap scan report for 192.168.30.1
Host is up (0.025s latency).
MAC Address: 00:24:C4:92:C3:21 (Cisco Systems)

Host script results:
|_sniffer-detect: Unknown (tests: "________")

Nmap scan report for 192.168.30.29
Host is up (0.069s latency).
MAC Address: 9C:4E:36:9E:36:2C (Intel Corporate)

Nmap scan report for 192.168.30.128
Host is up (0.024s latency).
MAC Address: EC:88:92:72:20:8C (Motorola Mobility, a Lenovo Company)

Host script results:
|_sniffer-detect: Unknown (tests: "_______1")

Nmap done: 256 IP addresses (3 hosts up) scanned in 12.06 seconds