555-1 waitfor delay '0:0:15' --

Short answer: In SQL Server, WAITFOR DELAY '0:0:15' pauses the batch for 15 seconds. The trailing -- is a SQL comment marker that would ignore the rest of the line if this payload were injected into a larger statement.

Details you can use for exam prep:

• Syntax

  • WAITFOR DELAY 'HH:MM:SS[.fraction]' is valid.
  • Example: WAITFOR DELAY '00:00:15' or WAITFOR DELAY '0:0:15' both mean 15 seconds.

• What it does

  • It suspends execution of the current batch/statement for the specified time.
  • If used in a multi-statement script, only the delay occurs at that point; subsequent statements wait until the delay finishes.

• Simple example

  • WAITFOR DELAY '00:00:15'; SELECT 1;
  • This would pause 15 seconds, then return 1.

• In the context of input that is injected into an application

  • A payload like "555-1; WAITFOR DELAY '00:00:15'; --" could cause the server to delay the response by 15 seconds.
  • The -- would comment out the rest of the original query, which is a classic effect of SQL injection payloads.

• Security and exam context

  • This technique is associated with time-based blind SQL injection.
  • Key defenses: use parameterized queries, stored procedures, input validation, least-privilege accounts, and proper error handling / logging.
  • Do not attempt to exploit in real systems; study this as a concept and defensive measure.

If you want, I can give a quick practice question or show how to measure an actual execution time in a safe test environment.