Certified Ethical Hacker (CEH) v13 312-50v13 — Question 197

An ethical hacker is hired to evaluate the defenses of an organization's database system which is known to employ a signature-based IDS. The hacker knows that some SQL Injection evasion techniques may allow him to bypass the system's signatures. During the operation, he successfully retrieved a list of usernames from the database without triggering an alarm by employing an advanced evasion technique. Which of the following could he have used?