Brute-force attacks are a hacking method in which an attacker systematically tries possible combinations of data, such as card numbers, expiration dates, CVV codes, or PINs, to find valid ones. This is especially relevant for payment systems, where cardholder data is a valuable target for fraudsters. Such attacks can be carried out automatically using scripts or botnets, allowing thousands of combinations to be tried per minute.
Multi-layered security strategies are used to prevent cardholder data from being guessed. These methods are based on security standards such as PCI DSS (Payment Card Industry Data Security Standard), which are designed to protect payment data. Below, I will examine key methods in detail, explaining their operating principles, advantages, potential drawbacks, and implementation examples. This will help you understand how they integrate into systems such as online stores, payment gateways (e.g., Stripe, PayPal), or banking applications. Please note that effective protection requires a combination of several methods, as one approach can be bypassed.
This protection not only prevents losses but also builds user trust. If you need code examples or specific tools, please inquire!
Multi-layered security strategies are used to prevent cardholder data from being guessed. These methods are based on security standards such as PCI DSS (Payment Card Industry Data Security Standard), which are designed to protect payment data. Below, I will examine key methods in detail, explaining their operating principles, advantages, potential drawbacks, and implementation examples. This will help you understand how they integrate into systems such as online stores, payment gateways (e.g., Stripe, PayPal), or banking applications. Please note that effective protection requires a combination of several methods, as one approach can be bypassed.
1. Rate Limiting
- How it works: The system sets a limit on the number of attempts to enter card data within a fixed time interval (e.g., 5 attempts per minute per IP address or account). Once the limit is exceeded, access is blocked for a specified period (lockout period), or additional verification is required.
- Why it works against brute force: Brute force relies on speed—thousands of attempts per second. Rate limiting reduces this speed to a level where the attack becomes economically unfeasible (it can take years to brute force a 16-digit card number).
- Advantages: Ease of implementation, low system load, does not interfere with legitimate users.
- Disadvantages: Attackers can bypass this using distributed attacks (from different IPs) or proxies. The solution is to combine it with other methods.
- Examples: In systems like Amazon Pay or Google Pay, after 3-5 incorrect CVV attempts, the system blocks the transaction for 10-30 minutes. In PCI DSS, this is requirement 10.2.4: Monitoring Failed Authentication Attempts.
2. Captcha and behavioral verification (CAPTCHA and Bot Detection)
- How it works: CAPTCHA (Completely Automated Public Turing test to tell computers and humans apart) requires the user to solve a task that is difficult to automate (for example, selecting images with specific objects). Modern versions, like Google's reCAPTCHA v3, analyze user behavior (mouse movements, typing speed) without an explicit task.
- Why it works: Brute force attacks are usually automated. CAPTCHA distinguishes bots from humans by blocking scripts.
- Advantages: Effective against simple bots; invisible versions do not irritate users.
- Disadvantages: Accessibility for people with disabilities; advanced bots (using AI) can bypass it. An alternative is honeypot fields (hidden fields that only bots can fill out).
- Examples: When paying on eBay or AliExpress, CAPTCHA appears after suspicious attempts. PCI DSS recommends this in requirement 8.5 to protect against automated attacks.
3. IP Blocking and Geo-Fencing
- How it works: The system monitors IP addresses and blocks those that are causing suspicious activity (for example, multiple failed transactions). Geofilters check location: if the card is from the US but the attempts are from another country, the transaction is blocked.
- Why it works: Attacks often come from anonymous or foreign IP addresses. This narrows the attack surface.
- Advantages: Fast response; integration with suspicious IP databases (e.g. from Cloudflare).
- Disadvantages: Legitimate VPN users may be blocked; attackers use proxies.
- Examples: Banks like Chase use geofilters: transactions from unusual regions require SMS confirmation. PCI DSS requirement 1.3: Network traffic control.
4. Tokenization and Data Masking
- How it works: Instead of storing or transmitting actual card data (PAN - Primary Account Number), a token is used—a random string associated with the data in secure storage. Masking reveals only a portion of the data (e.g., **** **** **** 1234).
- Why it works: Even if an attacker brute-forces tokens, they are useless without access to the storage. Brute-forcing the actual data is impossible.
- Benefits: Reduces the risk of data breaches; PCI DSS compliant (Requirement 3: Protecting Stored Data).
- Disadvantages: Requires integration with providers (for example, tokenization from Visa Token Service).
- Examples: Apple Pay uses tokens for each transaction, making them one-time use. This prevents the reuse of stolen data.
5. Multi-Factor Authentication (MFA)
- How it works: In addition to the card data, an additional factor is required: something that the user knows (password), has (SMS code, token) or is (biometrics, like a fingerprint).
- Why it works: Brute-forcing card data is useless without a second factor that changes dynamically.
- Benefits: High level of security; reduces phishing.
- Disadvantages: May slow down the payment process; problems with SMS delivery.
- Examples: 3D Secure (Verified by Visa, Mastercard SecureCode) is a standard for online payments where the bank sends an OTP (one-time password). In the EU, this is mandatory under PSD2.
6. Anomaly Detection and Machine Learning (Anomaly Detection and ML-based Systems)
- How it works: AI systems analyze patterns: typing speed, combination sequence, and the user's device. If behavior deviates from the norm (for example, thousands of attempts from a single device), the attack is blocked.
- Why it works: Detects complex attacks that bypass simple limits.
- Advantages: Adaptability; improves over time.
- Disadvantages: False positives; requires training data.
- Examples: PayPal's fraud detection uses ML to analyze transactions in real time. PCI DSS requirement 10.5: log monitoring.
7. Encryption and Secure Protocols
- How it works: Card data is encrypted (e.g., AES-256) during storage and transmission via TLS 1.3. This prevents data interception during transit.
- Why it works: Even if the data is intercepted, it is encrypted and cannot be brute-forced without the key.
- Benefits: Basic protection; required for all systems.
- Disadvantages: Does not protect against endpoint attacks.
- Examples: HTTPS with HSTS (HTTP Strict Transport Security) on sites like Shopify.
8. Throttling and Random Delays
- How it works: A delay (e.g. 1-5 seconds) is introduced between input attempts, or it is randomized to slow down the automation.
- Why it works: Increases attack time exponentially.
- Advantages: Simplicity; does not affect single attempts.
- Disadvantages: Can be annoying to users if errors occur.
- Examples: In banking applications, such as Sberbank, there are delays after entering an incorrect PIN.
9. Monitoring, Auditing, and Alerts Systems
- How it works: All transaction logs are analyzed in real time; if any suspicious activity (such as an increase in failed attempts) is detected, alerts are sent to administrators or users.
- Why it works: Allows you to respond quickly, blocking attacks at an early stage.
- Advantages: Integration with SIEM (Security Information and Event Management) systems.
- Disadvantages: Requires qualified personnel.
- Examples: Splunk or ELK Stack for monitoring at large banks. PCI DSS Requirement 10: Access Tracking.
10. Data Minimization and Standards Compliance
- How it works: Don't store sensitive data (CVV, PIN) at all; use tokens or external providers.
- Why it works: No data, no match.
- Benefits: Reduces risks; simplifies audit.
- Disadvantages: Dependence on third parties.
- Examples: PCI DSS Level 1 requires annual audits for large merchants.
Additional recommendations for educational purposes
- Combining methods: Use defense-in-depth: rate limiting + MFA + ML for multi-layered protection.
- Testing: Conduct penetration testing (ethically, with permission) to check for vulnerabilities.
- User education: Inform about risks, encourage the use of virtual cards (one-time numbers from banks).
- Current threats: AI bot attacks are on the rise in 2025, so focus on behavioral analysis.
- Resources for learning: Check out the PCI DSS documentation (pcisecuritystandards.org), the OWASP Cheat Sheet on brute-force, or Coursera courses on cybersecurity in finance.
This protection not only prevents losses but also builds user trust. If you need code examples or specific tools, please inquire!