A merchant acquirer has the need to store credit card numbers in a transactional database in a high
performance environment. Which of the following BEST protects the credit card data?

A.
Database field encryption

B.
File-level encryption

C.
Data loss prevention system

D.
Full disk encryption

Explanation:
Database encryption makes use of cryptography functions that are built into the database software to
encrypt the data stored in the data base. This often offers granular encryption options which allows for
the encryptions of the entire database, specific database tables, or specific database fields, such as a
credit card number field.
Incorrect Answers:
B: File-level encryption would involve encrypting the entire database file. This would mean that accessing
any data in the database would involve the overhead of decrypting the data.
C: A data loss prevention system is a system designed to detect a potential data breach. It is not used to
encrypt data.
D: Full disk encryption would involve encrypting the entire hard disk. This would mean that accessing any
data in the hard disk would involve the overhead of decrypting the data.

http://docs.oracle.com/cd/B28359_01/network.111/b28530/asotrans.htm#g1011122
Stewart, James Michael, CompTIA Security+ Review Guide, Sybex, Indianapolis, 2014, pp. 252-255