- Jan 17, 2017
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AI tools allow the analysis of old code, and find vulnerabilities that can be exploited
The Forgotten Code That's About to Expose Everything
Ryan McBeth
1.05M subscribers
Mar 14, 2026
View the article and original LinkedIn post at RyanMcBeth.substack.com.
For decades, a lot of the world’s most important computer systems were protected by something called security by obscurity. Not because they were secure… but because nobody remembered how they worked anymore.
In a recent LinkedIn post, Microsoft Azure CTO Mark Russinovich ran an experiment with Claude Code, an AI-powered development agent. He fed Claude a 1986 article about Applesoft BASIC programming.
Claude didn’t just understand the code. It reconstructed the programmer’s intent… and found a bug. That may not sound like a big deal. But it has enormous implications.
More than 70% of Fortune 500 companies still rely on legacy systems written in COBOL and other decades-old languages. Many of these systems were created long before modern cybersecurity practices existed.
For years they survived because the people who understood them retired or died.
But AI can now read, analyze, and reverse engineer software written 40 or even 50 years ago.
That means everything from banking systems and industrial controls to satellites and old corporate software could suddenly be scanned for vulnerabilities in minutes. And it’s not just governments that can do this. Anyone with access to modern AI tools could potentially start digging through legacy code looking for exploits.
The Forgotten Code That's About to Expose Everything
Ryan McBeth
1.05M subscribers
Mar 14, 2026
View the article and original LinkedIn post at RyanMcBeth.substack.com.
For decades, a lot of the world’s most important computer systems were protected by something called security by obscurity. Not because they were secure… but because nobody remembered how they worked anymore.
In a recent LinkedIn post, Microsoft Azure CTO Mark Russinovich ran an experiment with Claude Code, an AI-powered development agent. He fed Claude a 1986 article about Applesoft BASIC programming.
Claude didn’t just understand the code. It reconstructed the programmer’s intent… and found a bug. That may not sound like a big deal. But it has enormous implications.
More than 70% of Fortune 500 companies still rely on legacy systems written in COBOL and other decades-old languages. Many of these systems were created long before modern cybersecurity practices existed.
For years they survived because the people who understood them retired or died.
But AI can now read, analyze, and reverse engineer software written 40 or even 50 years ago.
That means everything from banking systems and industrial controls to satellites and old corporate software could suddenly be scanned for vulnerabilities in minutes. And it’s not just governments that can do this. Anyone with access to modern AI tools could potentially start digging through legacy code looking for exploits.
