What kind of attack is likely if the network passwords are common words and animal names?

The correct choice, which identifies the type of attack likely to occur with the use of common words and animal names as network passwords, is dictionary attacks. A dictionary attack is a method where an attacker attempts to gain unauthorized access by systematically entering every word in a predefined list or "dictionary" of possible passwords.

When passwords are simple and predictable, such as those that incorporate common terms or easily guessable names associated with animals, they become significantly vulnerable to this type of attack. Attackers can leverage dictionaries that include the most frequently used passwords or combinations that users might typically select, making it easier to guess the correct one.

The nature of dictionary attacks focuses on the weakness in the password choice rather than requiring extensive computational power to check every possible combination, which is characteristic of brute-force attacks. Therefore, when common words and animal names are employed as passwords, they fall directly into the type of security vulnerability exploited by dictionary attacks, making this the most applicable answer.