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 DIY solutions (like hardcoding VPN IP ranges) are unreliable and outdated quickly.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:

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

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.