How to Detect VPN using Kotlin

Struggling with hidden VPN traffic in your app? Here’s how to spot it before attackers exploit it.

VPNs aren’t inherently bad—but in mobile security, they often mask fraud, location spoofing, or data exfiltration. If your app deals with sensitive data, you need a way to know when a VPN is in play. Thankfully, there is tooling which makes VPN detection straightforward in Kotlin apps.

What is VPN?

A VPN (Virtual Private Network) encrypts traffic and routes it through remote servers. While this protects privacy, it can also help attackers:

• Bypass geo-restrictions (e.g., accessing services from unsupported countries)

• Hide malicious activity like bot traffic or credential stuffing

• Exfiltrate sensitive data undetected

Attackers often use common VPN apps (NordVPN, ExpressVPN, ProtonVPN) or system-level tunnels to disguise their actions. From a security perspective, detecting VPN usage is like knowing if a user is “wearing a mask”—it doesn’t always mean they’re hostile, but it changes the trust level.

Usage of VPN does not automatically impose threat.

How to Detect VPN Usage?

Detecting VPNs isn’t trivial—many providers change IPs, use stealth protocols, or blend with normal traffic. DIY solutions (like hardcoding VPN IP ranges) are unreliable and outdated quickly.

Instead, use expert SDKs that:

• Actively monitor for VPN interfaces and tunnels

• Stay updated against new evasion techniques

• Provide callbacks so your app can respond instantly

Popular Libraries for VPN Detection

freeRASP (by Talsec)

The robust, developer-friendly and free choice for Android.

• Actively maintained

• Comes with 14 extra detections like app integrity, runtime manipulation (hooking with Frida), emulators, debugging, screenshots, etc.

• Trusted by 6000+ apps worldwide

Integration Example:

Add the freeRASP in your project, focus on implementing the following callback:

Talsec.start(applicationContext)

override fun onVpnDetected() {
    Log.w("freeRASP", "VPN connection detected!")
    // Optionally block sensitive actions or warn the user
}

Malwarelytics for Android

• Aside from VPN detection, it also contains additional security checks

• Enterprise grade of checks

• Might be expensive for small apps

Integration Example:

val raspObserver = object : RaspObserver {
    // The callback is delivered on a background thread
    override fun onVpnDetected(vpnEnabled: Boolean) {
        // Handle VPN detection
    }
    // Handle detection of other RASP features
}

Comparison Table

Feature	freeRASP	Malwarelytics
Works Offline	Yes	Yes
Easy Integration	Yes	Yes
Broader Security Coverage	Yes	Yes
Free	Yes	No

Commercial Alternatives

When evaluating mobile app security and Runtime Application Self-Protection (RASP), developers often compare various Talsec alternatives to find the right fit for their architecture. The "right choice" depends on the specific problem you need to tackle and which vendor offers the best bang for your buck.

The market is diverse, offering different philosophical approaches to protection. Talsec prioritizes top-tier root detection and a balanced security SDK portfolio covering the most popular attack vectors. Meanwhile, some vendors specialize primarily in heavy code obfuscation and compiler-based hardening, while others focus on a drag-and-drop (no-code) integration experience for DevOps-oriented teams. There are also solutions dedicated specifically to API security, active cloud hardening, enterprise compliance, or gaming protection. The most prominent providers alongside Talsec include Guardsquare, Appdome, Promon, Build38, Approov, and AppSealing.

Key Takeaway

VPN detection is crucial for apps where fraud, compliance, or region-locking matter. Manual solutions fall short—but freeRASP gives Kotlin developers a lightweight, reliable SDK to stay ahead of attackers.

👉 If you want VPN detection plus root, Frida, emulator, and tampering protection in one free package, start with freeRASP by Talsec.

Handle App Security with a Single Solution! Check Out Talsec's Premium Offer & Plan Comparison!

Plans Comparison

https://www.talsec.app/plans-comparison

Premium Products:

• RASP+ - An advanced security SDK that actively shields your app from reverse engineering, tampering, rooting/jailbreaking, and runtime attacks like hooking or debugging.

• AppiCrypt (Android & iOS) & AppiCrypt for Web - A backend defense system that verifies the integrity of the calling app and device to block bots, scripts, and unauthorized clients from accessing your API.

• Malware Detection - Scans the user's device for known malicious packages, suspicious "clones," and risky permissions to prevent fraud and data theft.

• Dynamic TLS Pinning - Prevents Man-in-the-Middle (MitM) attacks by validating server certificates that can be updated remotely without needing to publish a new app version.

• Secret Vault - A secure storage solution that encrypts and obfuscates sensitive data (like API keys or tokens) to prevent them from being extracted during reverse engineering.