While "FHDA" likely refers to a specific target or internal tracking tag used by a security researcher or a tool, the string itself is a classic example of an . To prevent such attacks, developers should always use parameterized queries (prepared statements) rather than building queries with raw user input.
The -- (double dash) is the SQL syntax for a comment. Everything following these dashes is ignored by the database. This is used to "comment out" the rest of the original, legitimate code (like a closing quote or a WHERE clause) that would otherwise cause a syntax error and crash the attack. {KEYWORD}' UNION ALL SELECT NULL-- FHDA
The SELECT NULL part is often a "probe." For a UNION attack to work, the second query must have the exact same number of columns as the first. Attackers will add NULL values one by one (e.g., SELECT NULL, NULL-- ) until the page stops returning an error, which reveals how many columns are in the targeted table. 4. Commenting Out ( -- ) While "FHDA" likely refers to a specific target
The UNION ALL command is used to combine the results of two different SQL queries into a single result set. Attackers use this to trick a database into returning sensitive information (like usernames, passwords, or configuration data) that the user was never intended to see. 3. SELECT NULL Everything following these dashes is ignored by the database