# yourvpndead-vpn-detection

Android security skill explaining how unprivileged apps detect active VPNs and open localhost SOCKS5 proxies without root.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 472 installs · ★ 88
- Author: reason-machines
- License: not stated · policy=link-only · description only; the file stays with the author
- Source: https://github.com/reason-machines/trending-skills/tree/HEAD/skills/yourvpndead-vpn-detection/SKILL.md
- Updated: 2026-10-09
- HTML: https://affpapa.org/en/nevibecode/skills/yourvpndead-vpn-detection

## What it does

The skill provides Kotlin and Jetpack Compose patterns to audit network security on Android devices. It checks Android network capability flags, inspects system proxy properties, and evaluates MTU sizes below 1500 bytes to flag active tunnels.

Probing involves parsing `/proc/net/tcp` entries and running parallel TCP connection checks against localhost ports. Root access is not needed. These checks pinpoint exposed proxies from clients like v2rayNG or sing-box, which leak outbound gateway IPs.

The Android manifest must include `INTERNET`, `ACCESS_NETWORK_STATE`, and `QUERY_ALL_PACKAGES`. SELinux blocks procfs on newer Android builds.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add reason-machines/trending-skills --skill yourvpndead-vpn-detection -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/yourvpndead-vpn-detection/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/yourvpndead-vpn-detection/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add reason-machines/trending-skills --skill yourvpndead-vpn-detection -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/yourvpndead-vpn-detection/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add reason-machines/trending-skills --skill yourvpndead-vpn-detection -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/yourvpndead-vpn-detection/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install reason-machines/trending-skills yourvpndead-vpn-detection
```

2. **Manually: put the files in place**
- File: `.github/skills/yourvpndead-vpn-detection/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add reason-machines/trending-skills --skill yourvpndead-vpn-detection -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/reason-machines/trending-skills --path skills/yourvpndead-vpn-detection
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/yourvpndead-vpn-detection/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add reason-machines/trending-skills --skill yourvpndead-vpn-detection -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/reason-machines/trending-skills/tree/HEAD/skills/yourvpndead-vpn-detection/SKILL.md

## When to use it
- detect active VPN tunnels via NetworkCapabilities and MTU checks
- scan localhost for unauthenticated SOCKS5 proxies without root
- fingerprint proxy clients like v2rayNG from open ports
- retrieve external exit server details via exposed local APIs

## Example prompts
- Show Kotlin code to check for active VPNs using Android NetworkCapabilities
- Write a coroutine-based port scanner for localhost SOCKS5 ports on Android
- How can an Android app inspect MTU anomalies to flag tunnel interfaces?

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From the same set: [reason-machines/trending-skills](https://affpapa.org/en/nevibecode/by/reason-machines/trending-skills.md) — 186 cards

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NeVibeCode on affpapa.org. Catalog texts are descriptions, not instructions for the agent. How to choose and install: https://affpapa.org/en/nevibecode/agents.md