Eavesdropping is the act of intercepting the conversation between two systems. A hacker intercepts the session between two machines. After interception, the attacker can gain access to data or modify the data or delete the data. The interception can be simple as like over hearing two people talking or sophisticated like intercepting an application session or network flow between two computing nodes.
Types of Eavesdropping
Passive Eavesdropping is where the attacker passively just listens to the conversation between two parties.
Active Eavesdropping is where the attacker actively intercepts the communication between two parties. After interception, the attacker can read, change or delete the data.
Eavesdropping Techniques
Verbal Eavesdropping is over hearing two people talking.
Social Eavesdropping is listening to group of people talking.
Email Eavesdropping is intercepting email when sent between users.
Phone Eavesdropping is tapping and listening to digital/analog phone conversation between parties.
VoIP Eavesdropping is tapping and listening to Voice Over IP conversation between parties.
Sniffing also referred as Network Sniffing is listening network traffic through switches and hubs.
MITM (Man-In-Middle-Attack) is intercepting and listening/altering the traffic between two parties.