9 Attack techniques
9.1 Passive attacks

Passive attacks attempt to learn or make use of information from the system but do not affect system resources. A passive attack is one where the attacker only monitors the communication channel. A passive attacker only threatens the confidentiality of data.

Passive attacks are in the nature of eavesdropping on, or monitoring of, transmissions. The goal of the opponent is to obtain information that is being transmitted.

Two types of passive attacks are related to message contents and traffic analysis:

- Eavesdropping. In general, the majority of network communications occur in an unsecured or "plaintext" format, which allows an attacker who has gained access to data paths in the network to "listen in" or interpret (read) the data exchanged over the network. The ability of an eavesdropper to monitor the network is generally the biggest security problem that administrators face in an enterprise. Without strong encryption services that are based on cryptography, the data can be read by others as it traverses the network.
- Traffic analysis. It refers to the process of intercepting and examining messages in order to deduce information from patterns in communication. It can be performed even when the messages are encrypted and cannot be decrypted. In general, the greater the number of messages observed, or even intercepted and stored, the more can be inferred from the traffic.