Final answer:
The action of adding random data to passwords before storing them is called salting, which increases security by enhancing the unpredictability of password hashes.
Step-by-step explanation:
The technique being described in the question where a database administrator adds randomly generated data to each password before storing it is known as salting. This is a security measure that helps to protect passwords against certain types of attacks, such as dictionary attacks and rainbow table attacks. By adding a unique salt to each password, the complexity and unpredictability of password hashes is increased, making it significantly more difficult for an attacker to crack the passwords.
Key stretching is a related but distinct process where a password is processed using an algorithm that requires significant computational effort to produce a hash, slowing down brute-force attacks. Hashing is the transformation of a string of characters into a fixed-size value or key that represents the original string, which is more secure than plain text. Predictability does not refer to a security technique; rather, it is a concept that effective security measures seek to minimize to avoid easily guessable patterns.