Fuzzing and the quest for safer software

Fuzzing is an important method for finding bugs and security vulnerabilities in software. Read on to find out what fuzzing is and which methods are commonly used today.

It was a dark and stormy night. Bart Miller – you’ll find an interview with him at the end of our feature – was working at home, connected by 1200-baud modem to the University of Wisconsin’s mainframe computer. But every thunderclap meant that something went wrong: the lightning strikes disrupted data transmission over the phone line and garbled individual characters, forcing Miller to start over time and time again.

Each time he restarted, he noticed how many programs couldn’t cope with disrupted data – they crashed, hung up, or otherwise stopped working in some uncontrollable way. Shouldn’t programs do much better with invalid or glitched input? Miller decided to have his students systematically investigate this problem and gave them a programming assignment.

That night in the fall of 1988 is considered the birth of fuzz testing, by far the most important method today for testing programs for robustness and checking for security vulnerabilities. Professional programmers routinely use fuzzing to check for problems that could occur in the wild and might not be easy to anticipate. However, fuzzing is still a mystery to many part-time programmers and advanced users who program informally (including many in the Linux community). This month we take a close look at fuzzing and why it is so important.


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