Android App Login Bruteforce Prevention

TL;DR

Bruteforce attacks on Android app logins are common. This guide shows how to make your app more secure by implementing rate limiting, account lockout, strong password policies, and using reCAPTCHA or similar services.

1. Rate Limiting

Rate limiting restricts the number of login attempts from a single IP address or user account within a specific timeframe. This makes automated bruteforce attacks much slower and less effective.

1. Server-Side Implementation: Implement rate limiting on your backend server, not just in the app itself.
2. Track Attempts: Store login attempt data (IP address, user ID, timestamp).
3. Define Limits: Set reasonable limits (e.g., 5 attempts per minute from a single IP).
4. Reject Excess Requests: Return an error message if the rate limit is exceeded.

Example (Conceptual Python/Flask):

from flask import Flask, request, jsonify
import time

app = Flask(__name__)

login_attempts = {}

@app.route('/login', methods=['POST'])
def login():
    ip_address = request.remote_addr
    now = time.time()

    if ip_address in login_attempts:
        last_attempt = login_attempts[ip_address]
        if now - last_attempt < 60: # Within the last minute
            if len([a for a in login_attempts[ip_address] if a >= now - 60]) > 5:
                return jsonify({'message': 'Too many attempts. Please try again later.'}), 429
    
    # ... your actual login logic here...

    login_attempts[ip_address] = now
    return jsonify({'message': 'Login successful!'})

2. Account Lockout

After a certain number of failed login attempts, temporarily lock the account to prevent further brute-forcing.

1. Track Failed Attempts: Store the number of failed login attempts for each user account.
2. Lockout Threshold: Define a threshold (e.g., 5 failed attempts).
3. Lock Account: When the threshold is reached, disable the account.
4. Lockout Duration: Set a lockout duration (e.g., 15 minutes, 1 hour).
5. Unlock Mechanism: Provide a way to unlock the account (e.g., email verification, support request).

3. Strong Password Policies

Enforce strong password requirements to make passwords harder to crack.

• Minimum Length: Require a minimum password length (e.g., 8 characters).
• Complexity: Enforce complexity rules (uppercase, lowercase, numbers, symbols).
• Password History: Prevent users from reusing previous passwords.
• Regular Updates: Encourage or require regular password changes.

4. Two-Factor Authentication (2FA)

Add an extra layer of security by requiring a second factor of authentication (e.g., SMS code, authenticator app).

1. Implementation: Integrate a 2FA provider into your app.
2. Enable/Disable: Allow users to enable or disable 2FA.
3. Recovery Codes: Provide recovery codes in case the user loses access to their second factor.

5. reCAPTCHA or Similar Services

Use a CAPTCHA service like reCAPTCHA to distinguish between human users and bots.

• Integration: Integrate reCAPTCHA into your login form.
• Invisible reCAPTCHA: Consider using Invisible reCAPTCHA for a better user experience.

6. Secure Communication (HTTPS)

Always use HTTPS to encrypt communication between the app and the server, protecting credentials from interception.

• SSL/TLS Certificate: Ensure your server has a valid SSL/TLS certificate.
• Force HTTPS: Redirect all HTTP traffic to HTTPS.

7. Obfuscate Code

While not foolproof, code obfuscation can make it harder for attackers to reverse engineer your app and identify security vulnerabilities.

8. Regular Security Audits

Conduct regular security audits of your app and server-side code to identify and fix potential vulnerabilities.