Scanning underlying source code with a database of regular expressions to quickly identify suspicious code, application inputs, outputs etc primarily relates to ..

White-box testing involves analyzing the actual source code, byte code, or binary of an application to identify security vulnerabilities, coding errors, and suspicious patterns. Using regular expressions (regex) to scan code for known vulnerability patterns, dangerous function calls, or tainted data flow is a classic white-box static analysis technique. Black-box testing only tests the running application without code access, while grey-box combines both approaches.