[2] Sniffing attacks can be compared to tapping of phone wires and get to know about the conversation, and for this reason, it is also referred as wiretapping applied to computer networks.
Using sniffing tools, attackers can sniff sensitive information from a network, including email (SMTP, POP, IMAP), web (HTTP), FTP (Telnet authentication, FTP Passwords, SMB, NFS) and many more types of network traffic.
Packet sniffers can just watch, display, and log the traffic, and this information can be accessed by the attacker.
In case there is a necessity for using any insecure protocol in any application, all the data transmission should be encrypted.
If required, VPN (Virtual Private Networks) can be used to provide secure access to users.