You’ve probably been there. You’re trying to buy concert tickets, log into your bank, or just post a comment, and suddenly you’re blocked. ‘Access denied: suspicious activity.’ You’re not a hacker. You’re not a bot. You’re just sitting in a coffee shop or using your phone’s cellular data.
If you build or maintain any online service, you probably think your IP blacklists are protecting you. You think proxy detection is a solved problem. It’s not. The game has fundamentally changed, and the tools you’re using are stuck in the past.
The internet was built on the lie that one IP address equals one human. In the age of CGNAT, that lie is breaking everything.
Take a look at a new tool making the rounds called ‘Proxy-or-Not.’ It’s a humble attempt to detect residential proxies—the sneaky networks bad actors use to hide their true locations. The creator notes it successfully catches major proxy networks like SOAX and BrightData. But the comments section immediately exposes the dirty secret of modern network security.
A user reports: ‘My provider is correct but the VPN detected is a false positive.’ This isn’t a bug in the code. It’s the fundamental paradox of Carrier-Grade NAT (CGNAT).
ISPs ran out of IPv4 addresses years ago, so they started putting hundreds, sometimes thousands, of innocent users behind a single shared IP address. Proxy providers do the exact same thing. From the outside looking in, a legitimate user on AT&T and a malicious bot routing through a residential proxy look virtually identical.
Every time you tighten the net to catch a proxy, you inevitably strangle a legitimate user sharing the exact same network.
If you’re running fraud detection, content licensing, or rate limiting, this tool’s limitations should terrify you. Without a massive, constantly updated training set of behavioral data, accuracy remains incredibly fragile. You can’t just check a static list of ‘bad’ IPs anymore. The bad guys are rotating through residential IPs that belong to real people.
This isn’t a static classification problem. It’s a behavioral arms race. The proxy services are constantly adapting their patterns to mimic normal human traffic. If your defense relies on outdated IP reputation scores, you’re fighting a 2010 war in 2024.
Proxy detection isn’t a static classification problem; it’s a behavioral arms race where the innocent are always caught in the crossfire.
Stop blindly trusting IP blacklists. Accept that IP addresses are no longer a reliable proxy for identity. If you don’t evolve your security posture to look at behavioral patterns, session anomalies, and device fingerprints, you aren’t stopping the fraudsters. You’re just blocking your best customers.
FAQ
Q: If IP blacklists don't work, what am I supposed to use to stop bots?
A: You need to layer your defenses. Combine IP reputation with behavioral biometrics, device fingerprinting, and session analysis. Stop looking at the IP in isolation and start looking at how the user interacts with your application.
Q: Why do ISPs use CGNAT if it causes all these security headaches?
A: Because we ran out of IPv4 addresses. CGNAT allows ISPs to cram thousands of users behind a single public IP. It's a necessary evil of the modern internet, and it's exactly why IP-based trust models are fundamentally broken.
Q: Is it even possible to detect residential proxies without false positives?
A: Not with 100% accuracy, and anyone who tells you otherwise is lying. The goal isn't elimination; it's risk scoring. You have to accept a certain threshold of false positives, or you'll lock out legitimate users by the thousands.