That string looks like an SQL-injection payload. Breakdown:
- The arithmetic: 2+909-909-1 = 1 and 0+0+0+1 = 1, so the equality 2+909-909-1 = 0+0+0+1 is true.
- The OR therefore makes the whole condition true.
- The trailing -- is the SQL line comment marker (it comments out the rest of the SQL on that line), so anything after it is ignored.
Typical use: if injected into a WHERE clause like
SELECT * FROM users WHERE username = '';
it can turn the WHERE into a tautology (always true) and bypass authentication or return all rows.
I can’t help you perform attacks, but if your goal is defensive (testing your own app or fixing a vulnerability), here are recommended mitigations:
- Use parameterized queries / prepared statements instead of string concatenation for SQL.
- Use an ORM or a library that enforces parameterization.
- Validate and whitelist input (type, length, allowed characters) where practical.
- Escape values only as a last resort and with the DB-specific escaping function.
- Run the DB account with least privileges (don’t use a high-privilege account for app queries).
- Use stored procedures carefully (they can help, but are not a substitute for parameterization).
- Enable application logging and monitor for suspicious input patterns.
- Put a Web Application Firewall (WAF) in front of the app for added protection.
- Use static analysis and dependency scanning to find common injection patterns.
If you want, tell me the language/framework you’re using and I can show a short secure example of parameterized queries or help review a specific vulnerable snippet.