Eavesdropping in the cybersecurity world refers to the interception of communication between two parties by a malicious third party (hackers). Eavesdropping is similar to a sniffing attack, where software applications allow a hacker to steal usernames and passwords simply by observing network traffic. This often happens on Public Wi-Fi networks where it is relatively easy to spy on weak or unencrypted traffic or by putting up a fake Wi-Fi network for unsuspecting users to connect to.
In all three situations, hackers are eavesdropping on your communications seeking to steal login credentials, and other sensitive information on a user’s devices. Eavesdropping also allows hackers to listen into VoIP communications as well. Eavesdropping is often conducted by deploying “Stalkerware” onto unsuspecting users devices, often by someone you know (family member).
Source: ECPI University
Additional Reading: How Hackers Use An Ordinary Light Bulb To Spy On Conversations 80 Feet Away