Which of the following is the ability to hide messages in existing data?

The correct answer, which is the ability to hide messages in existing data, is steganography. Steganography involves concealing a message within another medium—such as an image, audio file, or text—so that it remains hidden from those who are not aware of its existence. By integrating the hidden message into the fabric of the carrier file, steganography provides a layer of secrecy that differs from cryptography, which focuses on disguising the content of the message itself rather than hiding its presence.

In contrast to steganography, cryptography transforms information into an unreadable format that can only be deciphered by someone with the appropriate key or password. Although both methods serve the purpose of securing information, steganography emphasizes concealment, while cryptography emphasizes obfuscation of content.

Scareware typically refers to malware designed to frighten users into purchasing unnecessary software or services through misleading alerts about imaginary threats; it does not pertain to hiding messages within data. Whaling, on the other hand, is a type of phishing attack specifically targeting high-profile individuals within an organization and is unrelated to the practice of hiding messages.

Therefore, steganography clearly aligns with the definition given in the question, making it the correct answer.