{keyword}' Union All Select Null-- Fhda -

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.

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 ( -- ) {KEYWORD}' UNION ALL SELECT NULL-- FHDA

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

The initial ' (single quote) is used to "break out" of a predefined data field in a website's code. If the application isn't properly sanitizing inputs, this quote tells the database that the original command has ended and a new one is beginning. 2. The UNION ALL Operator The SELECT NULL part is often a "probe

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