Detailed documentation on identifying and preventing these vulnerabilities can be found through the OWASP Foundation or PortSwigger's Web Security Academy. Blind SQL Injection Detection and Exploitation (Cheatsheet)
The text you provided is a common string used in attacks, specifically a Time-Based attack targeting Microsoft SQL Server. What this code does {KEYWORD}) WAITFOR DELAY '0:0:5' AND (8141=8141
: This is a "tautology"—a statement that is always true. It is used by attackers to ensure the logic of the injected code doesn't break the original query. {KEYWORD}) WAITFOR DELAY '0:0:5' AND (8141=8141