A passive attack is an information security event or incident based on monitoring or scanning communications, information flows or systems. In some cases, passive attacks are difficult to detect because they simply monitor as opposed to trying to break into a system. The following are illustrative examples.
Tapping
Monitoring unencrypted communications such as emails or telephone calls.
Encryption
Intercepting encrypted information flows and trying to break the encryption.
Scanning
Scanning a device connected to the internet for vulnerabilities such as open ports or a weak operating system version.
Traffic Analysis
Monitoring internet traffic to build data such as who is visiting what website.
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