Eavesdropping is listening in on communications. Eavesdropping can be the recording of network traffic using a packet-capturing tool, generically known as a sniffer (FIGURE 2-6). Hackers can eavesdrop against data packets or against voice traffic. Eavesdropping can occur over wired or wireless connections.

Any communication performed in plain and directly usable data forms is subject to interception and recording. You can prevent eavesdropping by using encrypted protocols. Only strongly cryptographically encoded messages are safe from outsiders learning the content of the conversation. But as super computers gain speed and efficiency, the ability to crack encryption is only a matter of time once the packets are acquired.