Question

555'||DBMS_PIPE.RECEIVE_MESSAGE(CHR(98)||CHR(98)||CHR(98),15)||'

Answer 1

That string is an Oracle/SQL payload that causes a blocking/time-delay when evaluated. Breakdown:

- CHR(98) is the ASCII character "b", so CHR(98)||CHR(98)||CHR(98) → "bbb".
- DBMS_PIPE.RECEIVE_MESSAGE(name, timeout) is an Oracle call that waits for a message on the named pipe for up to timeout seconds and returns an integer status (typically 0 on success, non‑zero for timeout/failure).
- The expression 555'||DBMS_PIPE.RECEIVE_MESSAGE(CHR(98)||CHR(98)||CHR(98),15)||' concatenates "555" with the integer result of RECEIVE_MESSAGE (Oracle will implicitly convert the integer to text).

Effect:
- If no message arrives on pipe "bbb", RECEIVE_MESSAGE will block for up to 15 seconds and then return a timeout code. The overall expression therefore delays the query by ~15 seconds and yields something like "5551" (or "555" + whatever non‑zero status code).
- If a message is present immediately, RECEIVE_MESSAGE returns success quickly (status 0) and the expression yields "5550" (no delay).

Why attackers use this:
- It’s a time‑based blind SQL injection technique to detect whether arbitrary PL/SQL calls are possible and to infer truth by measuring response delays.

Notes / caveats:
- DBMS_PIPE requires the package to be present and EXECUTE privileges (and some environments restrict or disable it), so it won’t work everywhere.
- The exact numeric return codes can vary; the important behavior is that non‑success typically indicates timeout and can be detected by timing.

Mitigations / detections:
- Use parameterized queries / bind variables; avoid concatenating untrusted input into SQL.
- Remove or revoke unnecessary EXECUTE rights on DBMS_PIPE (and other PL/SQL packages) from application schemas.
- Defense in depth: input validation/whitelisting, least privilege, application-layer sanitization, WAF rules to block such payloads.
- Monitor for slow/blocked queries or unusual calls to DBMS_* packages and add logging/alerts for long-running queries.

If you intended this for testing, make sure you have explicit permission to test the target. If you want, I can help describe safe ways to test for time‑based injection or how to harden a specific Oracle setup.