Anthropic-Cybersecurity-Skills/skills/detecting-mobile-malware-behavior/scripts/agent.py

#!/usr/bin/env python3
"""Mobile malware behavior detection agent.

Analyzes Android APK manifests and iOS app metadata for suspicious permissions,
dangerous API usage, and known malware behavioral patterns.
"""

import argparse
import json
import re
import subprocess
import zipfile
from pathlib import Path
from datetime import datetime

DANGEROUS_ANDROID_PERMISSIONS = {
    "android.permission.SEND_SMS": ("HIGH", "Can send SMS (premium rate fraud)"),
    "android.permission.READ_SMS": ("HIGH", "Reads SMS (OTP theft)"),
    "android.permission.RECEIVE_SMS": ("HIGH", "Intercepts SMS"),
    "android.permission.READ_CONTACTS": ("MEDIUM", "Reads contacts"),
    "android.permission.RECORD_AUDIO": ("HIGH", "Records audio"),
    "android.permission.CAMERA": ("MEDIUM", "Camera access"),
    "android.permission.READ_CALL_LOG": ("HIGH", "Reads call logs"),
    "android.permission.ACCESS_FINE_LOCATION": ("MEDIUM", "Fine GPS location"),
    "android.permission.WRITE_EXTERNAL_STORAGE": ("LOW", "Write to external storage"),
    "android.permission.INSTALL_PACKAGES": ("CRITICAL", "Can install other apps"),
    "android.permission.REQUEST_INSTALL_PACKAGES": ("HIGH", "Request app install"),
    "android.permission.SYSTEM_ALERT_WINDOW": ("HIGH", "Overlay attacks"),
    "android.permission.BIND_ACCESSIBILITY_SERVICE": ("CRITICAL", "Accessibility abuse"),
    "android.permission.BIND_DEVICE_ADMIN": ("CRITICAL", "Device admin control"),
    "android.permission.READ_PHONE_STATE": ("MEDIUM", "Reads device identifiers"),
    "android.permission.PROCESS_OUTGOING_CALLS": ("HIGH", "Intercepts outgoing calls"),
}

SUSPICIOUS_RECEIVERS = [
    "BOOT_COMPLETED", "SMS_RECEIVED", "PHONE_STATE",
    "NEW_OUTGOING_CALL", "PACKAGE_ADDED", "CONNECTIVITY_CHANGE",
]

MALWARE_API_PATTERNS = [
    (r"DexClassLoader|PathClassLoader", "HIGH", "Dynamic code loading"),
    (r"Runtime\.exec|ProcessBuilder", "HIGH", "Command execution"),
    (r"TelephonyManager\.getDeviceId", "MEDIUM", "Device fingerprinting"),
    (r"Base64\.decode.*exec", "CRITICAL", "Encoded payload execution"),
    (r"loadLibrary|System\.load", "MEDIUM", "Native library loading"),
    (r"Cipher.*AES.*encrypt", "LOW", "Encryption (possible ransomware)"),
    (r"javax\.crypto", "LOW", "Cryptographic operations"),
    (r"HttpURLConnection|OkHttp", "LOW", "Network communication"),
    (r"getRuntime\(\)\.exec", "HIGH", "Shell command execution"),
]


def analyze_apk_manifest(apk_path):
    findings = []
    permissions = []
    try:
        result = subprocess.run(
            ["aapt", "dump", "permissions", apk_path],
            capture_output=True, text=True, timeout=30)
        if result.returncode == 0:
            for line in result.stdout.split("\n"):
                perm_match = re.search(r"uses-permission.*'([^']+)'", line)
                if perm_match:
                    perm = perm_match.group(1)
                    permissions.append(perm)
                    if perm in DANGEROUS_ANDROID_PERMISSIONS:
                        sev, desc = DANGEROUS_ANDROID_PERMISSIONS[perm]
                        findings.append({
                            "type": "dangerous_permission",
                            "permission": perm,
                            "severity": sev,
                            "description": desc,
                        })
    except (FileNotFoundError, subprocess.TimeoutExpired):
        try:
            with zipfile.ZipFile(apk_path, 'r') as z:
                if "AndroidManifest.xml" in z.namelist():
                    findings.append({"note": "Binary manifest found, use aapt or apktool to decode"})
        except zipfile.BadZipFile:
            findings.append({"error": "Invalid APK file"})

    return {"permissions": permissions, "findings": findings}


def scan_decompiled_source(source_dir):
    findings = []
    source_path = Path(source_dir)
    for java_file in source_path.rglob("*.java"):
        try:
            content = java_file.read_text(encoding="utf-8", errors="replace")
            for pattern, severity, desc in MALWARE_API_PATTERNS:
                matches = re.findall(pattern, content)
                if matches:
                    findings.append({
                        "type": "suspicious_api",
                        "file": str(java_file),
                        "pattern": desc,
                        "match_count": len(matches),
                        "severity": severity,
                    })
        except OSError:
            continue
    for smali_file in source_path.rglob("*.smali"):
        try:
            content = smali_file.read_text(encoding="utf-8", errors="replace")
            if "Landroid/app/admin/DeviceAdminReceiver" in content:
                findings.append({
                    "type": "device_admin",
                    "file": str(smali_file),
                    "severity": "CRITICAL",
                    "description": "App registers as device administrator",
                })
        except OSError:
            continue
    return findings


def calculate_risk(findings):
    score = 0
    for f in findings:
        sev = f.get("severity", "LOW")
        score += {"CRITICAL": 30, "HIGH": 15, "MEDIUM": 5, "LOW": 2}.get(sev, 0)
    risk = "CRITICAL" if score >= 80 else "HIGH" if score >= 40 else \
           "MEDIUM" if score >= 15 else "LOW"
    return {"score": min(score, 100), "risk_level": risk}


def main():
    parser = argparse.ArgumentParser(description="Mobile Malware Behavior Detector")
    parser.add_argument("--apk", help="Path to APK file")
    parser.add_argument("--source-dir", help="Path to decompiled source directory")
    args = parser.parse_args()

    results = {"timestamp": datetime.utcnow().isoformat() + "Z", "findings": []}

    if args.apk:
        apk_results = analyze_apk_manifest(args.apk)
        results["permissions"] = apk_results["permissions"]
        results["findings"].extend(apk_results["findings"])

    if args.source_dir:
        results["findings"].extend(scan_decompiled_source(args.source_dir))

    results["risk"] = calculate_risk(results["findings"])
    results["total_findings"] = len(results["findings"])
    print(json.dumps(results, indent=2))


if __name__ == "__main__":
    main()