Final answer:
Piggybacking is the act of gaining unauthorized access to a secure area by following an authorized person.
Step-by-step explanation:
Gaining unauthorized access to the data center by using another user's credentials when following them into the building is an example of piggybacking.
Piggybacking is a social engineering technique where an unauthorized person gains access to a secure area by following an authorized person, taking advantage of their legitimate access.
In the context of data centers, piggybacking can lead to security breaches and compromise the integrity and confidentiality of sensitive data.