Question

555*if(now()=sysdate(),sleep(3),0)

Answer 1

This looks like a MySQL expression (commonly seen in time-based SQL injection tests). Breakdown:

- IF(now() = sysdate(), sleep(3), 0)
- now() returns the statement-start timestamp (constant for the statement).
- sysdate() returns the current time at the moment it is evaluated (not constant).
- IF(condition, a, b) evaluates and returns a if condition true, otherwise b.
- SLEEP(3) causes the server thread to pause for 3 seconds and returns 0 on success.

- 555 * (that IF(...) result)
- The multiplication forces numeric context. Because SLEEP() returns 0 when it succeeds, the numeric result will be 0 whether the IF chooses the SLEEP branch or the 0 branch — but the SLEEP branch has the side effect of delaying execution.

Practical effect
- If now() = sysdate() evaluates true, the server will pause about 3 seconds (due to SLEEP(3)) and then the expression yields 0 (so 555*0 = 0).
- If the condition is false, no sleep happens and the expression yields 0 immediately.
- Whether the condition is true depends on timing/precision and MySQL version; comparing now() and sysdate() is not a reliable way to get a deterministic true/false across environments.

Security note
- This pattern is often used in time-based SQL injection probes to detect whether a condition holds by observing a delay. Discussing or testing such probes should be done only on systems you own or are authorized to test.
- To prevent exploitation: use parameterized queries/prepared statements, strict input validation/whitelisting, least-privilege DB accounts, WAFs and query logging/monitoring for unusual delays or SLEEP calls.

If you want, tell me the context (are you debugging a query, analyzing a log entry, or hardening an app?) and I can give targeted advice (how it will behave in your MySQL version, safe tests you can run locally, or secure coding mitigations).