What is the purpose of fuzzers in application security testing?

Fuzzers are tools specifically designed to enhance application security by providing invalid, unexpected, or random data as input to software. The primary objective of using fuzzers is to uncover vulnerabilities that may not be found through typical testing methods. By deliberately feeding an application erroneous or malformed data, fuzzers can trigger faults, crashes, or unexpected behaviors. This process ultimately helps identify weaknesses that could be exploited by attackers, paving the way for developers to address these security issues before they can be leveraged maliciously.

The focus of fuzzing is not merely on the exploitation of vulnerabilities, which would imply taking advantage of discovered weaknesses. Instead, fuzzers aim to discover those weaknesses in the first place. Simulating real user input is also a valuable aspect of testing, but it does not encompass the core objective of fuzzing, which is about pushing the boundaries of application inputs to find vulnerabilities. Static code analysis, on the other hand, involves examining source code without executing the program, which contrasts with how fuzzers operate by interacting with running applications.