-1' OR 3*2>999 --

Short explanation:

• This string is a classic-looking SQL injection payload.
• In a vulnerable query, it would typically be used like: ... WHERE something = '$input'; If input is -1' OR 32>999 --, the query becomes: ... WHERE something = '-1' OR 32>999 --
• Evaluate the boolean: 3*2 > 999 is 6 > 999, which is false.
• The double dash -- starts a comment, so the rest of the statement is ignored.
• So the WHERE clause effectively becomes something = '-1' OR FALSE. That reduces to something = '-1'. If a row with something = '-1' exists, it would return that row; otherwise it returns nothing.
• This is not a guaranteed bypass. A true bypass payload would typically use something like ' OR 1=1 --, which makes the condition always true.

Key takeaways for exams:

• 3*2 > 999 evaluates to false.
• -1' ends a string literal; the following OR ... is the injected condition.
• -- comments out the rest of the query.
• To bypass authentication reliably, attackers often use ' OR 1=1 -- (or similar), which yields true.

Defensive best practices:

• Use parameterized queries / prepared statements (no string concatenation of user input).
• Validate and sanitize input; apply least-privilege database accounts.
• Use ORM with binding of parameters.
• Web application firewalls can help, but rely on proper query handling first.
• Regular security testing in a safe environment (e.g., with a test DB and approved test cases).

If you want, I can walk through more payloads and show how they behave in different SQL dialects (MySQL, PostgreSQL, SQL Server).